Definition of sub-chantress in English:
sub-chantress
noun ˌsʌbˈtʃɑːntrɪsˌsʌbˈtʃɑːntrɛsˌsʌbˈtʃantrɪs
Christian Church historical A nun who assists the precentor of a convent.
Origin
Late Middle English. From sub- + chantress. Compare Old French souschantre.