|Definition - A word that can mean opposite things — more precisely, a word that has a homograph that is an antonym.|
(1) cleave (to cut apart) and cleave (to seal together)
(2) dust (remove dust) and dust (apply dust, say for fingerprints)
(3) moot (arguable) and moot (not worthy of argument)
Etymology - The term derives from the name of the Roman god Janus, the guardian of portals, as well as beginnings and endings. He is usually depicted as having two opposed faces.