The Collaborative International Dictionary of English v.0.48:
Vicenary \Vic"e*na*ry\ (?; 277), a. [L. vicenarius, fr. viceni twenty each; akin to viginti twenty.] Of or pertaining to twenty; consisting of twenty. [1913 Webster]WordNet (r) 3.0 (2006):
vicenary adj 1: of or relating to or based on 20