In the Catholic liturgy at the dismissal, the Latin phrase used is "Ite, missa est." The usual translation for this is "Go, the Mass has ended."
Can someone suggest a proper parsing of this somewhat opaque phrase?
The phrase is confusing if one assumes that missa is a perfect passive participle, since it has no obvious antecedent. The ending dialogue of the (Pauline/Novus Ordo) mass goes,
V: Benedicat vos Omnipotens Deus: Pater, Filius et Spiritus Sanctus.
V: Ite, missa est.
R: Deo gratias.
One could guess that it is the benedictio that is sent. But in the older form of the mass, this blessing does not come until after the Ite missa est (the Ita missa est is preceded only by Dominus vobiscum / Et cum spiritu tuo). One might guess that the antecedent is something else like ecclesia or congregatio, but any proposed answer would be at best a guess. There is no sure historical answer. There was no liturgical committee from, say, the fourth century that composed this form out of nothing and wrote down exactly what they were thinking when they did.
The more probably and generally accepted answer is that missa in this case is probably not a perfect passive participle at all. It is just an alternative form of the noun missio, i.e. dismissal. The Catholic Encyclopedia provides some analogous cases.
Before it became the technical name of the holy Liturgy in the Roman Rite, it meant simply "dismissal". The form missa for missio is like that of collecta (for collectio), ascensa (ascensio), etc. So Ite missa est should be translated "Go it is the dismissal."
So missa is just a first declension, singular, nominative noun, meaning, "dismissal."
This comes from Dom Prosper Guéranger's Explanation of the Prayers and Ceremonies of Holy Mass:
ITE MISSA EST.
These words are usually translated thus: “Go, the Mass is said.” However, we must here observe that this is not their proper sense. This formula, adopted by the Church, was in general use amongst the Romans, in public assemblies, to announce the termination of the meeting. So, these words: Ite, concio missa est, meant “go, the assembly is dismissed.”
In the early ages, the Holy Sacrifice was never called by our word Missa, the Mass. When the Sacrifice was finished, the assembled faithful were dismissed by the Deacon, in the form usual at all public meetings. Later, the word missa having been adopted, the confusion of ideas became complete, when by the putting of a capital M to this formula, it ended in Ite Missa est, being thus translated amiss: Go, the Mass is said. In Masses at penitential times, in Lent, for example, instead of the Ite Missa est, the Deacon says Benedicamus Domino; the faithful are not dismissed, because it is supposed that they would like to remain longer in prayer, during these days of expiation. The Ite Missa est is consequently a sign of joy, and, as such, it is excluded from Requiem masses: a Song of joy would be out of keeping with a Mass breathing only sadness and supplication.
The Ite Missa est having been said, the Priest turns again to the Altar, and bowing somewhat, with his hands joined, he says: Placeat tibi Sancta Trinitas obsequium servtutis meae, et praesta ut Sacrificium, quod oculis tuae majestatis indignus obtuli, tibi sit acceptabile, mihique et omnibus, pro quibus illud obtuli, sit, te miserante, propitiabile. Per Christum Dominum nostrum. Amen. This prayer is a kind of epitome made by the Priest, reminding the Holy Trinity of all he has just been doing, begging acceptance of this Sacrifice, and that it may be profitable to all those for whom he has been praying.
We had a very detailed (if somewhat ill-tempered) discussion of this issue in another forum. It is not easy to summarise the line of thought, so it might be better just to have a look at it: