Te Deum : An ancient and celebrated Christian hymn, of uncertain authorship, but often ascribed to St. Ambrose; -- so called from the first words "Te Deum laudamus." It forms part of the daily matins of the Roman Catholic breviary, and is sung on all occasions of thanksgiving. In its English form, commencing with words, "We praise thee, O God," it forms a part of the regular morning service of the Church of England and the Protestant Episcopal Church in America.

Te Deum : A religious service in which the singing of the hymn forms a principal part.

Example:


Taxonomy
Te Deum, hymn, God, O Lord, Domine, praise thee, free encyclopedia, praise, gloria, Sanctus, Te Deum laudamus, Christian hymn, hymn of praise, Christ, Tibi, the Father, Latin, the Church.

Defination from the web:
Te Deum is sung at the end of the Office of Readings on days when the Gloria is sung (in this case ... Sir William Walton's Coronation Te Deum was written for the coronation of HM Queen Elizabeth II in 1952. ...