fool around \fool` a*round"\, v. i. [imp. & p. p. Fooled around; p. pr. & vb. n. Fooling around.]

1. To waste time in idle pursuits; to fool[2].

Syn: fool[2]. [PJC]

2. To flirt or philander. --RHUDbr/ [PJC]

3. To be sexually promiscuous; to engage in sexual intercourse with more than one partner; especially, to engage in adultery; as, to fool around with another woman. [PJC]

Source: The Collaborative International Dictionary of English v.0.48
 

64 Moby Thesaurus words for "fool around": antic, be foolish, be stupid, caper, caracole, carry on, cavort, clown, clown around, coquet, curvet, cut a dido, cut capers, cut up, dabble, dally, dance, disport, fiddle, fiddle with, fiddle-faddle, fidget with, finger with, flirt, flounce, fool, fool with, fribble, frisk, frivol, frolic, gambol, get funny, go haywire, horse around, idle, invite ridicule, jerk off, kid around, loiter, mess around, monkey, monkey around, piddle, play, play around, play the buffoon, play the fool, play with, potter, putter, rollick, romp, skip, smatter, sport, tinker, tomfool, toy, toy with, trifle, trip, twiddle, womanize

Source: Moby Thesaurus II by Grady Ward, 1.0
 

fool around

Source: WordNet (r) 2.0