Definition from Wiktionary, the free dictionary
Alternative forms 
trapdoor (plural trapdoors)
- A hinged or sliding door set into a floor or ceiling.
- (theater) Such a trap set into the floor of a stage to allow fast exits and entrances.
- (computing) A secret method of obtaining access to a program or online system; a backdoor.
- (mathematics, cryptography) The special information that permits the inverse of a trapdoor function to be easily computed.
Derived terms 
door set into floor or ceiling
similar door on a stage
secret access to a program
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