clyster UK /ˈklɪstə/US /ˈklɪstɚ/ noun1 •(no longer used) A medicine applied via the rectum; an enema or suppository.Cnelius a physician being sent for, found his costiveness alone to be the cause, and thereupon gave him a clyster, by which he was speedily recovered. — 2001 formsclysters