The Collaborative International Dictionary of English v.0.48:

Booby \Boo"by\ (b[=oo]"b[y^]), n.; pl. Boobies (-b[i^]z). [Sp.
   bobo dunce, idiot; cf. L. balbus stammering, E. barbarous.]
   [1913 Webster]
   1. A dunce; a stupid fellow.
      [1913 Webster]

   2. (Zool.)
      (a) A swimming bird (Sula fiber or Sula sula) related
          to the common gannet, and found in the West Indies,
          nesting on the bare rocks. It is so called on account
          of its apparent stupidity -- unafraid of men, it
          allows itself to be caught by a simple and undisguised
          approach. The name is also sometimes applied to other
          species of gannets; as, Sula piscator, the
          red-footed booby; and Sula nebouxii, the
          blue-footed booby.
      (b) A species of penguin of the antarctic seas.
          [1913 Webster]

   Booby hatch
      (a) (Naut.), a kind of wooden hood over a hatch, readily
          removable.
      (b), an insane asylum. [Colloq.]

   Booby hut, a carriage body put upon sleigh runners. [Local,
      U. S.] --Bartlett.

   Booby hutch, a clumsy covered carriage or seat, used in the
      eastern part of England. --Forby.

   Booby prize, an award for the poorest performance in a
      competition; hence, metaphorically, the recognition of a
      strikingly inferior or incompetent performance.

   Booby trap
      (a), a schoolboy's practical joke, as a shower bath when a
          door is opened.
      (b), any concealed device causing surprise or injury when
          a usually harmless object is touched; -- in military
          operations, typically containing an explosive charge.
          [1913 Webster +PJC]

WordNet (r) 3.0 (2006):

booby trap
    n 1: an explosive mine hidden underground; explodes when stepped
         on or driven over [syn: land mine, ground-emplaced
         mine, booby trap]
    2: an unforeseen or unexpected or surprising difficulty [syn:
       pitfall, booby trap]

Moby Thesaurus II by Grady Ward, 1.0:

26 Moby Thesaurus words for "booby trap":
   Dionaea, ambuscade, ambush, ambushment, baited trap, blind,
   deadfall, deathtrap, decoy, firetrap, flytrap, gin, lurking hole,
   mine, mole trap, mousetrap, pitfall, rattrap, set gun, shadowing,
   spring gun, springe, stalking-horse, surveillance, trap,
   trapfall