verb (funs, funning, funned)North American informal
late 17th century (denoting a trick or hoax): from obsolete fun 'to cheat or hoax', dialect variant of late Middle English fon 'make a fool of, be a fool', related to fon 'a fool', of unknown origin. Compare with fond
The use of fun as an adjective meaning ‘enjoyable,’ as in we had a fun evening, is now established in informal use, although not accepted in standard English. The comparative and superlative forms funner and funnest, formed as if fun were a standard adjective, should only be used in very informal contexts, typically speech.