auto-antonym

An auto-antonym (sometimes spelled autantonym), or contronym (also spelled contranym), is a word with a homograph (another word of the same spelling) which is also an antonym (a word with the opposite meaning). An auto-antonym is alternatively called an antagonym, Janus word (after the Roman god), enantiodrome, self-antonym, antilogy, or addad (Arabic, singular didd). It is a word with multiple meanings, one of which is defined as the reverse of one of its other meanings. This phenomenon is called enantiosemy, enantionymy or antilogy.