The Collaborative International Dictionary of English v.0.48:

Mantrap \Man"trap`\, n.
   1. A trap for catching trespassers. [Eng.]
      [1913 Webster]

   2. A dangerous place, as an open hatch, into which one may
      fall.
      [1913 Webster]

WordNet (r) 3.0 (2006):

mantrap
    n 1: a very attractive or seductive looking woman [syn:
         smasher, stunner, knockout, beauty, ravisher,
         sweetheart, peach, lulu, looker, mantrap, dish]
    2: a trap for catching trespassers