RhymeZone: trapdoor definitions

Definitions of trapdoor:

noun: A hinged or sliding door set into a floor or ceiling.
noun: (theater) Such a trap set into the floor of a stage to allow fast exits and entrances.
noun: (computing) A secret method of obtaining access to a program or online system; a backdoor.
noun: (mathematics, cryptography) The special information that permits the inverse of a trapdoor function to be easily computed.
noun: (mining) A door in a level for regulating the ventilating current; a weather door.

(Definitions from Wiktionary)