epispastic noun 2adjective 1forms 3 noun2 •(old-fashioned) A vesicant agent; that which causes blisters. •(old-fashioned) A blister. adjective1 •(no longer used) Causing blisters; vesicant.Old Postle says this: "Cantharides when used internally are diuretic and stimulant; when applied externally they are epispastic and rubefacient." Now what the devil can he mean, eh? — 1960 formsepispastics · more epispastic · most epispastic