Adjective: mordant mor-d(u)ntHarshly ironic or sinisterfun ranging from slapstick clowning ... to savage mordant wit; - black, grim Of a substance, especially a strong acid; capable of destroying or eating away by chemical action - caustic, corrosive, erosive, vitriolicNoun: mordant mor-d(u)ntA substance used to treat leather or other materials before dyeing; aids in dyeing processSounds like: m