Definition of "fun"

fun

/fʌn/

noun
uncountable
1. Amusement, enjoyment or pleasure.
  Quotations
  Grafting your boss's face onto the hind end of a donkey is fun, but serious fun is when you create the impossible and it looks real.
  2000, Robert Stanley, The Complete Idiot's Guide to Adobe Photoshop 6, Alpha Books, page 377
2. Playful, often noisy, activity.
adjective
comparative more fun or funner, superlative most fun or funnest
1. (informal) Enjoyable or amusing.
  Quotations
  He's the liberated character that everyone wants to be, so he was very fun to play
  2016 January 11, Tom Bateman, quoted in Nigel Hunt, "Jekyll and Hyde, TV revamp of Robert Louis Stevenson classic, debuts on CBC-TV" CBC News, Canada
2. (informal) Whimsical or flamboyant.
verb
third-person singular simple present funs, present participle funning, simple past and past participle funned
1. (colloquial) To tease, kid, poke fun at, make fun of.