contronym

 
Pronunciation: /ˈkɒntrənɪm/
(also contranym)

noun

  • a word with two opposite meanings, e.g. sanction (which can mean both ‘a penalty for disobeying a law’ and ‘official permission or approval for an action’).

Origin:

1960s: blend of contra- and -onym, on the pattern of synonym and antonym