The Collaborative International Dictionary of English v.0.48:

Wing it \Wing it\, v. i.
   To perform an act, such as to give a speech, without the
   usual preparation. To improvise or ad-lib.
   [1913 Webster]

Moby Thesaurus II by Grady Ward, 1.0:

52 Moby Thesaurus words for "wing it":
   ad-lib, be getting along, buzz off, come away, cook up, dash off,
   depart, do offhand, exit, extemporize, fake, gang along, get along,
   get away, get off, get on, get under way, go, go along, go away,
   go off, go on, improvisate, improvise, jury-rig, knock off,
   lash up, leave, make up, march off, mosey, move away, move off,
   move out, play by ear, pull out, sashay, sashay off,
   scrap the plan, stagger along, strike off, take flight, take wing,
   throw off, throw together, toddle along, toss off, toss out,
   up and go, vamp, whip up, whomp up