WordNet sense 1 (the matter ejected in vomiting):

barf, puke, vomitus

WordNet sense 2 (a medicine that induces nausea and vomiting):

emetic, nauseant, vomitive

WordNet sense 3 (the reflex act of ejecting the contents of the stomach through the mouth):

disgorgement, regurgitation, emesis, puking, vomiting

WordNet sense 4 (eject the contents of the stomach through the mouth):

cast, cat, chuck, disgorge, honk, purge, regurgitate, retch, sick, spew, upchuck, regorge, spue, be sick, throw up, vomit up