Contronym

A contronym is a word with more than one meaning (sense), as one meaning is the reverse (opposite) of the other. For example, the word cleave can mean "to cut apart" or "to bind together". In a sentence its meaning can be clear, otherwise the word itself is ambiguous. Contronyms are also known as auto-antonyms.

Many other words are polysemic, because they have more than one meaning. However, most polysemic words are not contronyms.

• Other examples:
• to sanction may mean to approve or to punish;
• To overlook can mean to miss seeing something, or to see it but act as if nothing had happened.
• Fast: to move quickly, or be stuck in one place.