Definition of "trapdoor"

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

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

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

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

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

(cryptography, transitive) To subvert (a cryptographic scheme) by means of a secret parameter that makes the trapdoor function easy to compute.  examples

(surgery, intransitive) To form a trapdoor deformity.  examples