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1.
(n.)

A sixth sense that only the wisest and most foolish people have; The awareness to events that lead to trickery and deception.

Commonly found in amphibians.
Mon Calamari: Admiral! We have enemy ships in sector 47!

Admiral Ackbar: (trapdar senses tingling) It's a trap!

(source: IMDB.com , "Star Wars: Episode VI - Return of the Jedi")
by BaTycoon April 06, 2011
 
2.
Similar to how a gaydar is the ability to detect non-heterosexuality, the trapdar is the ability to detect a trap--that is, a male who can be easily mistaken for a female.
<A> That chick's pretty hot, I should ask her out.
<B> Don't. That "chick" is setting off my trapdar.
by Rei^2 August 14, 2009