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.

plural of trapdoor

Any spider, of the family Ctenizidae, that constructs a silk-lined burrow with a hinged lid.

plural of trapdoor spider

(mathematics, cryptography) A function that is easy to compute in one direction but difficult to compute in the opposite direction (finding its inverse) without special information.

plural of trapdoor function

Any spider of the superfamily Cyrtauchenioidea, which build burrows but lack the thorn-like spines on the outermost leg segments common to true trapdoor spiders.

plural of wafer trapdoor spider