Fun  —n. 1 lively or playful amusement. 2 source of this. 3 mockery, ridicule (figure of fun). —attrib. Adj. Colloq. Amusing, enjoyable (a fun thing to do).  for fun (or for the fun of it) not for a serious purpose. In fun as a joke, not seriously. Make fun of (or poke fun at) ridicule, tease. [obsolete fun, fon: related to *fond]