From The Collaborative International Dictionary of English v.0.48 [gcide]:
2. (R. C. Ch.) (a) A psalm sung or chanted immediately before the collect, epistle, and gospel, and while the priest is entering within the rails of the altar. (b) A part of a psalm or other portion of Scripture read by the priest at Mass immediately after ascending to the altar.
From WordNet (r) 3.0 (2006) [wn]:
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