switchblade

A folding knife with a sliding or pivoting blade contained in the handle which is extended automatically by a spring when a button, lever, or switch on the handle or bolster is activated.

Virtually all switchblades incorporate a locking blade, a means of preventing the blade from being accidentally closed while in the open position. An unlocking mechanism must be activated in order to close the blade for storage.

Also known as a switch knife, automatic knife, pushbutton knife, ejector knife, flick knife, gravity knife, flick blade, or spring knife.