n. - A going in.
n. - A psalm sung or chanted immediately before the collect, epistle, and gospel, and while the priest is entering within the rails of the altar.
n. - A part of a psalm or other portion of Scripture read by the priest at Mass immediately after ascending to the altar.
n. - An anthem or psalm sung before the Communion service.
n. - Any composition of vocal music appropriate to the opening of church services.