The Collaborative International Dictionary of English v.0.48:
Conventual \Con*ven"tu*al\ (?; 135), a. [LL. conventualis: cf. F. conventuel.] Of or pertaining to a convent; monastic. "A conventual garb." --Macaulay. [1913 Webster] Conventual church, a church attached or belonging to a convent or monastery. --Wordsworth. [1913 Webster]