Merriam-Webster's Collegiate® Dictionary, 11th Edition
FUN
I. noun
Etymology: English dialect fun to hoax, perhaps alteration of Middle English fonnen, from fonne dupe
Date: 1727
what provides amusement or enjoyment, a mood for finding or making amusement ,
3. amusement , enjoyment , derisive jest ; sport , ridicule , violent or excited activity or argument , Synonyms: see: fun
II. intransitive verb (funned; funning)
Date: 1833
to indulge in banter or play ; joke ,
III. adjective (sometimes funner; sometimes funnest)
Date: circa 1846
providing entertainment, amusement, or enjoyment , full of fun ; pleasant