1.AdjectiveOf the side of the chancel, apse, altar or choir on which the cantor's (later precentor's) stall is placed (the left hand side to a person facing the altar);
"the cantoris side of a choir; a cantoris stall"
2.NounThe lower of two choral voice parts sung when a part splits into two; traditionally sung by members of the choir on the cantoris side.
3.NounThat half of the choir singing cantoris parts, collectively.