hy·dro·gen·ate \-āt, usu -ād.+V\transitive verb (-ed/-ing/-s) Etymology:hydrogen + -ate 1.: to combine with hydrogen < hydrogenate a vegetable oil to a fat > 2.: to treat with or expose to hydrogen < hydrogenate rosin > — compare harden vt 1a • hy·dro·gen·a·tor\-ād.ə(r)\noun-s