Trapdoor

Part of speech: noun (n.)

1. A lifting or sliding door covering an opening in a roof or floor.

2. A door in a level for regulating the ventilating current; -- called also weather door. Raymond. Trapdoor spider (Zoöl.), any one of several species of large spiders which make a nest consisting of a vertical hole in the earth, lined with a hinged lid, like a trapdoor. Most of the species belong to the genus Cteniza, as the California species (C. Californica).