what is a 'spiritual communion'?

For those who cannot have access to the Holy Mass and Holy Communion, I commend the devout practice of Spiritual Communion. When we are rightly disposed to receive Holy Communion, that is, when we are in the state of grace, not conscious of any mortal sin which we have committed and for which we have not yet been forgiven in the Sacrament of Penance, and desire to receive Our Lord in Holy Communion but are unable to do so, we unite ourselves spiritually with the Holy Sacrifice of the Mass, praying to Our Eucharistic Lord in the words of Saint Alphonsus Liguori: “Since I am unable now to receive Thee sacramentally, come at least spiritually into my heart.” Spiritual Communion is a beautiful expression of love for Our Lord in the Blessed Sacrament. It will not fail to bring to us abundant grace. —Cardinal Raymond Leo Burke
Various Acts of Spiritual Communion
Traditional Prayer by St. Alphonsus Liguori:
My Jesus, I believe that You are present in the Most Holy Sacrament. I love You above all things, and I desire to receive You into my soul. Since I cannot at this moment receive You sacramentally, come at least spiritually into my heart. I embrace You as if You were already there and unite myself wholly to You. Never permit me to be separated from You. Amen.
Another Act of Spiritual Communion:
O Jesus, I turn toward the holy tabernacle where You live hidden for love of me. I love you, O my God. I cannot receive you in Holy Communion. Come, nevertheless, and visit me with Your grace. Come spiritually into my heart. Purify it. Sanctify it. Render it like unto Your own. Lord, I am not worthy that you should enter under my roof, but only say the word and my soul shall be healed. Amen.
Cardinal Merry del Val’s Spiritual Communion Prayer:
At your feet, O my Jesus, I prostrate myself and I offer you repentance of my contrite heart, which is humbled in its nothingness and in your holy presence. I adore you in the Sacrament of your love, the ineffable Eucharist. I desire to receive you into the poor dwelling that my heart offers you. While waiting for the happiness of sacramental communion, I wish to possess you in spirit. Come to me, O my Jesus, since I, for my part, am coming to you! May your love embrace my whole being in life and in death. I believe in you, I hope in you, I love you. Amen.
St. Vincent Pallotti’s Spiritual Communion Prayer:
Jesus, Infinite Love, truly God and truly man, my food and drink, I desire you and I wish to desire you with the fullness of love with which you are desired by the Angels, the Saints, and their Queen, the Most Holy Mary, with the fullness of love of her own heart. And relying on your infinite mercy which does not reject even the most miserable—indeed it seeks them out, I wish to receive you in every moment, forever; and I wish to make as many acts of love and adoration as you deserve and for all the goals that are pleasing to you. Amen.
A Spiritual Communion based on a Latin poem:
I desire, O my Jesus, that you would refresh me on this the food of angels: Make me, my kind Jesus, always worthily approach to this divine repast. Let this food be a nutriment, let this drink be a nourishment, be unto my soul: Let it give grace while I breathe, in my final agony be it a pledge of future glory. Amen.
A Marian Spiritual Communion Prayer:
O Immaculate Queen of Heaven and Earth, Mother of God and Mediatrix of every grace: I believe that Thy dearly beloved Son, Our Lord Jesus Christ, is truly, really, and substantially contained in the Most Blessed Sacrament. I love Him above all things and I long to receive Him into my heart. Since I cannot now receive Him sacramentally, be so good as to place Him spiritually in my soul. O my Jesus, I embrace Thee as One who has already come, and I unite myself entirely to Thee. Never permit me to be separated from Thee. Amen.
Spiritual Communion Prayer of Mother Teresa:
O God, we believe you in the Eucharist. We adore you and love you with our whole heart and soul because you are most worthy of all our love. We desire to love you as the blessed do in heaven. Flood our souls with your spirit and life. Penetrate and possess our whole being utterly, that our lives may only be a radiance of yours. Shine through us, and be so in us that every soul we come in contact with may feel your presence in our soul. Amen.
Longer Spiritual Communion Prayer:
As I cannot this day enjoy the happiness of assisting at the holy Mysteries, O my God! I transport myself in spirit at the foot of Thine altar; I unite with the Church, which by the hands of the priest, offers Thee Thine adorable Son in the Holy Sacrifice; I offer myself with Him, by Him, and in His Name. I adore, I praise, and thank Thee, imploring Thy mercy, invoking Thine assistance, and presenting Thee the homage I owe Thee as my Creator, the love due to Thee as my Savior.
Apply to my soul, I beseech Thee, O merciful Jesus, Thine infinite merits; apply them also to those for whom I particularly wish to pray. I desire to communicate spiritually, that Thy Blood may purify, Thy Flesh strengthen, and Thy Spirit sanctify me. May I never forget that Thou, my divine Redeemer, hast died for me; may I die to all that is not Thee, that hereafter I may live eternally with Thee. Amen.
My Jesus, I believe that You are present in the Most Holy Sacrament. I love You above all things, and I desire to receive You into my soul. Since I cannot at this moment receive You sacramentally, come at least spiritually into my heart. I embrace You as if You were already there and unite myself wholly to You. Never permit me to be separated from You. Amen.
Another Act of Spiritual Communion:
O Jesus, I turn toward the holy tabernacle where You live hidden for love of me. I love you, O my God. I cannot receive you in Holy Communion. Come, nevertheless, and visit me with Your grace. Come spiritually into my heart. Purify it. Sanctify it. Render it like unto Your own. Lord, I am not worthy that you should enter under my roof, but only say the word and my soul shall be healed. Amen.
Cardinal Merry del Val’s Spiritual Communion Prayer:
At your feet, O my Jesus, I prostrate myself and I offer you repentance of my contrite heart, which is humbled in its nothingness and in your holy presence. I adore you in the Sacrament of your love, the ineffable Eucharist. I desire to receive you into the poor dwelling that my heart offers you. While waiting for the happiness of sacramental communion, I wish to possess you in spirit. Come to me, O my Jesus, since I, for my part, am coming to you! May your love embrace my whole being in life and in death. I believe in you, I hope in you, I love you. Amen.
St. Vincent Pallotti’s Spiritual Communion Prayer:
Jesus, Infinite Love, truly God and truly man, my food and drink, I desire you and I wish to desire you with the fullness of love with which you are desired by the Angels, the Saints, and their Queen, the Most Holy Mary, with the fullness of love of her own heart. And relying on your infinite mercy which does not reject even the most miserable—indeed it seeks them out, I wish to receive you in every moment, forever; and I wish to make as many acts of love and adoration as you deserve and for all the goals that are pleasing to you. Amen.
A Spiritual Communion based on a Latin poem:
I desire, O my Jesus, that you would refresh me on this the food of angels: Make me, my kind Jesus, always worthily approach to this divine repast. Let this food be a nutriment, let this drink be a nourishment, be unto my soul: Let it give grace while I breathe, in my final agony be it a pledge of future glory. Amen.
A Marian Spiritual Communion Prayer:
O Immaculate Queen of Heaven and Earth, Mother of God and Mediatrix of every grace: I believe that Thy dearly beloved Son, Our Lord Jesus Christ, is truly, really, and substantially contained in the Most Blessed Sacrament. I love Him above all things and I long to receive Him into my heart. Since I cannot now receive Him sacramentally, be so good as to place Him spiritually in my soul. O my Jesus, I embrace Thee as One who has already come, and I unite myself entirely to Thee. Never permit me to be separated from Thee. Amen.
Spiritual Communion Prayer of Mother Teresa:
O God, we believe you in the Eucharist. We adore you and love you with our whole heart and soul because you are most worthy of all our love. We desire to love you as the blessed do in heaven. Flood our souls with your spirit and life. Penetrate and possess our whole being utterly, that our lives may only be a radiance of yours. Shine through us, and be so in us that every soul we come in contact with may feel your presence in our soul. Amen.
Longer Spiritual Communion Prayer:
As I cannot this day enjoy the happiness of assisting at the holy Mysteries, O my God! I transport myself in spirit at the foot of Thine altar; I unite with the Church, which by the hands of the priest, offers Thee Thine adorable Son in the Holy Sacrifice; I offer myself with Him, by Him, and in His Name. I adore, I praise, and thank Thee, imploring Thy mercy, invoking Thine assistance, and presenting Thee the homage I owe Thee as my Creator, the love due to Thee as my Savior.
Apply to my soul, I beseech Thee, O merciful Jesus, Thine infinite merits; apply them also to those for whom I particularly wish to pray. I desire to communicate spiritually, that Thy Blood may purify, Thy Flesh strengthen, and Thy Spirit sanctify me. May I never forget that Thou, my divine Redeemer, hast died for me; may I die to all that is not Thee, that hereafter I may live eternally with Thee. Amen.