The Collaborative International Dictionary of English v.0.48:
Vesicant \Ves"i*cant\, n. [L. vesica blister: cf. F. v['e]sicant.] (Med.) A vesicatory. [1913 Webster]WordNet (r) 3.0 (2006):
vesicant adj 1: causing blisters [syn: vesicatory, vesicant] n 1: a chemical agent that causes blistering (especially mustard gas) [syn: vesicant, vesicatory]