The Collaborative International Dictionary of English v.0.48:

aerialist \aer"i*al*ist\ n.
   1. an athlete who performs acts high above the ground on a
      trapeze or high wire, requiring skill and agility and
      coordination.

   Syn: trapeze artist
        [WordNet 1.5 +PJC]

   2. a burglar who gains entrance to buildings from the
      rooftop, sometimes leaping from building to building in
      the process. A type of second-story man. [Slang]
      [PJC]

WordNet (r) 3.0 (2006):

aerialist
    n 1: an acrobat who performs in the air (as on a rope or
         trapeze)

Moby Thesaurus II by Grady Ward, 1.0:

25 Moby Thesaurus words for "aerialist":
   acrobat, bareback rider, circus artist, clown, contortionist,
   equestrian director, equilibrist, flier, funambulist, gymnast,
   high wire artist, high-wire artist, juggler, lion tamer,
   palaestrian, pancratiast, ringmaster, ropewalker,
   slack-rope artist, snake charmer, sword swallower,
   tightrope walker, trapeze artist, tumbler, weightlifter