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Webster 1913 Edition

Noun.

A trap for catching trespassers.

[Eng.]

A dangerous place, as an open hatch, into which one may fall.

See also: man-trap

mantrap ‎(plural mantraps)

A mechanical device for catching trespassers.
A small space with two sets of interlocking doors, such that the first set of doors must close before the second set opens, used to restrict access.
(slang) A woman who is dangerously seductive to men.
- 2011, J. F. Bone, The Lani People
  If anything, she was worse since she had enough money to implement her desires. They were merely in the trade for business reasons. No—Eloise would be something to steer clear of. Alexander was right. She was a mantrap.