switchblades

n. spring-operated pocket knife which is opened by pushing a button on its handle

A switchblade [1] (also known as automatic knife, switch, or in British English flick knife) is a type of knife with a folding or sliding blade that springs out of the grip when a button or lever on the grip is pressed. Switchblades are illegal weapons in many jurisdictions, often covered by very specific laws—many of which appear to have been enacted at times of  moral panic by newspapers and films about supposed knife use. This was most striking in the late 1950s, when films such as The Wild One in 1954, Rebel Without a Cause and High School Confidential in 1955, and the Broadway play West Side Story in 1957 about rebellious youth featured switchblades, and were closely followed by the US Switchblade Act of 1958 (a federal law; individual state laws differ widely). This US federal law was closely followed by the UK Restriction of Offensive Weapons Act 1959.
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Noun
1. a pocketknife with a blade that springs open at the press of a button
(synonym) switchblade knife, flick knife
(hypernym) pocketknife, pocket knife

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