(sometimes capitalized) Long-standing nickname of a complicated, seemingly man-made excavation on Oak Island in Nova Scotia, Canada, rumored to contain pirate treasure and which has been repeatedly and unsuccessfully probed at great expense.

(anatomy) A deep ciliated fossa on the dorsal midline of the buccal cavity in lancelets.

Any of various venomous snakes of the family Crotalinae, found in Asia and the Americas, with a deep pit or groove on either side of the head which enables them to detect prey by infrared sensing; a pit viper.

plural of pit adder

Alternative form of pit adder

(now rare) The eye socket; the concave area of the face around each eye.

(military) A trench for sheltering sharpshooters.

The bottom of the abdomen

A pit filled with snakes. / (figuratively) Any institution (such as a school, prison, hospital, etc.) run in an inept or inhumane way, or full of hostile or treacherous people.

(historical) An enclosed space into which rats are placed to be killed by a dog for sport.