= pipe key n. at pipe, n.1 compounds 2.

a key with a hollow barrel which fits over a pin in a lock; cf. pipe lock n.

A special key of a door or gate giving privileged access, esp. a key which operates any one of a number of locks, a master key (also figurative); a…

a key having a hollow stem, the end of which is of a rose-shaped pattern.

(a) a wrench designed to grasp or fit over the head of a nut, screw-bolt, etc., and turn it; = screw wrench n.; (b) a key cut with a spiral thread.

(a) a key that can be put on a finger; (b) a key fitted with a ring handle, which falls down instead of standing out from the lock.

In full Chubb's lock, Chubb-lock: a patent lock with tumblers and, in addition, a lever called a detector, which fixes the bolt immovably when one…

A small key.

†(a) a card featuring a list or diagram explaining the figures in a picture, the symbols used in a book, etc.; cf. key, n.1 5d (obsolete); (b) a…

Originally U.S. A card which acts as a key in providing access to something or in operating a device; (now) spec. a plastic card on which data is…