noun a going in.
2. introit ·noun an anthem or psalm sung before the communion service.
3. introit ·noun any composition of vocal music appropriate to the opening of church services.
4. introit ·noun a part of a psalm or other portion of scripture read by the priest at mass immediately after ascending to the altar.
5. introit ·noun a psalm sung or chanted immediately before the collect, epistle, and gospel, and while the priest is entering within the rails of the altar.