trapdoor

noun

1. A hinged or sliding door set into a floor or ceiling.

2. (theater) Such a trap set into the floor of a stage to allow fast exits and entrances.

3. (computing) A secret method of obtaining access to a program or online system; a backdoor.

4. (mathematics, cryptography) The special information that permits the inverse of a trapdoor function to be easily computed.

5. (mining) A door in a level for regulating the ventilating current; weather door.