The Collaborative International Dictionary of English v.0.48:

Pitfall \Pit"fall`\, n.
   A pit deceitfully covered to entrap wild beasts or men; a
   trap of any kind. --Sir T. North.
   [1913 Webster]

WordNet (r) 3.0 (2006):

pitfall
    n 1: an unforeseen or unexpected or surprising difficulty [syn:
         pitfall, booby trap]
    2: a trap in the form of a concealed hole [syn: pit,
       pitfall]

Moby Thesaurus II by Grady Ward, 1.0:

48 Moby Thesaurus words for "pitfall":
   Dionaea, bait, baited trap, booby trap, catch, cobweb, coral heads,
   danger, deadfall, deathtrap, decoy, difficulty, entanglement,
   firetrap, flytrap, gin, hazard, ironbound coast, ledges, lee shore,
   lure, meshes, mine, mole trap, mousetrap, peril, pit, quicksands,
   rattrap, risk, rockbound coast, rocks, sandbank, sandbar, sands,
   set gun, shallows, shoals, snag, snare, spring gun, springe, toils,
   trap, trapfall, undercurrent, undertow, web