button lock

Noun

 * 1) A type of lock (for knives, and other tools, of folding or collapsing type) in which the lock is released with the press of a button, usually on the side of the handle; such a lock often allows the tool to be locked closed as well as locked open.
 * 2)  A knife or other tool with such a lock.

Usage notes
Although the control surface of almost any type of lock for folding knives (lockback, liner lock, or otherwise) might reasonably be viewed as a button in natural terms, there is a conventional distinction in the definition of a button lock whereby the button is a distinct part, usually on the side of the handle, and the mechanism is different from a liner lock or lockback mechanism. Part of this distinction is that the button often can engage the lock in both the closed and open positions, which is not true of liner lock or lockback mechanisms, at least in their usual and archetypal forms. The assumptions that any locking folder is a "lockback", or that any lock with any control surface comparable to a button is a "button lock", sometimes cause confusion.