According to http://www.music.vt.edu/musicdictionary/, "gloria in excelsis Deo" means "Glory to God in heaven."

The Latin expression comes from Luke 2:14 ""Glory to God in the highest" (the literal Greek is "Splendor to God in the highest") In the Old testament we are given one of many descriptive names for God, by God. In Deuteronomy 26:19 we read of "El-Elyon" - the “high, uppermost, exalted” one (more commonly “most high”). As early as Genesis 14:18-21 it is recorded that King Melchizedek was called a “priest of El-elyon” and in Genesis 14:22 Abram spoke of "Yahweh, El-ELyon" ("I Am, most high"). The angelic proclaimation as recorded in the gospel (literally "good message") of Luke was a doxology proclaiming that the same God of the Old Testament was responsible for sending the promised Messiah. There are some other biblical references, with this highly exalted state in mind, which refer to God's dominon and power as the supreme ruler of heaven and earth. Deuteronomy 10:14 To the LORD your God belong the heavens, even the highest heavens, the earth and everything in it. 2 Chronicles 2:6 But who is able to build a temple for him, since the heavens, even the highest heavens, cannot contain him? 2Chronicles 6:18 "But will God really dwell on earth with men? The heavens, even the highest heavens, cannot contain you. How much less this temple I have built! Nehemiah 9:6 You alone are the LORD. You made the heavens, even the highest heavens, and all their starry host, the earth and all that is on it, the seas and all that is in them. You give life to everything, and the multitudes of heaven worship you. Psalm 148:4 Praise him, you highest heavens and you waters above the skies.

Gloria in excelsis Deo, et in terra pax hominibus bonae voluntatis. Glory to God in the highest and peace to men of good will, or Glory to God in the highest, and peace to His people on earth. A Latin doxology that is the second item of the Ordinary of the Roman Catholic Mass and begins with the words Gloria in excelsis Deo. Gloria in excelsis Deo means Glory to God in the highest.

Cantate "Gloria in Excelsis Deo" by George Friedrich Handel for solo soprano - lost and then discovered at the end of the twentieth century. Listen to Vera Trifanova singing all six pieces of Gloria at http://www.veratrifanova.com/en/audio or at http://www.youtube.com/watch?v=_nmEqQbcmcI Below is the text in English and Latin: Latin Glória in excélsis Deo et in terra pax homínibus bonae voluntátis. Laudámus te, benedícimus te, adorámus te, glorificámus te, grátias ágimus tibi propter magnam glóriam tuam, Dómine Deus, Rex cæléstis, Deus Pater omnípotens. Dómine Fili Unigénite, Iesu Christe, Dómine Deus, Agnus Dei, Fílius Patris, qui tollis peccáta mundi, miserére nobis; qui tollis peccáta mundi, súscipe deprecatiónem nostram. Qui sedes ad déxteram Patris, miserére nobis. Quóniam tu solus Sanctus, tu solus Dóminus, tu solus Altíssimus, Iesu Christe, cum Sancto Spíritu: in glória Dei Patris. Amen. English Glory be to God on high. And in earth peace towards men of good will. We praise thee. We bless thee. We worship thee. We glorify thee. We give thanks to thee for thy great glory. O Lord God, heavenly King God the Father almighty. O Lord, the only-begotten Son Jesu Christ. O Lord God, Lamb of God, Son of the Father. Thou that takest away the sins of the world, have mercy upon us. Thou that takest away the sins of the world, receive our prayer. Thou that sittest at the right of the Father, have mercy upon us. For thou only art Holy. Thou only art the Lord. Thou only art the Most High. Thou only, O Jesu Christ, with the Holy Ghost, art Most High in the glory of God the Father. Amen.

(Latin) "Glory to God on high."

Literally translated: In Exaltation of God