To raise, hoist, or lift a thing using a jack, or similar means. / (informal) To raise, increase, or accelerate; often said of prices, fees, or rates.

A jack on a wall used to connect a telephone to the telephone line.

A jack on a wall used to connect a television to the cable television service.

plural of Cracker Jack

simple past tense and past participle of jack up

Hoisted, lifted off the ground, or propped up using a jack. / (slang, automotive) Describes a 4x4 automobile that has a "lift kit", raising the body and/or frame higher than stock.

Alternative form of jumping jack

A compact folding knife. / The front-dive pike, in which the body folds and unfolds. / (colloquial) A semi-trailer truck accident in which the vehicle mimics the closing of a jack-knife.

To fold in the middle, as a jackknife does. / (colloquial) To cause a semi-trailer truck to fold like a jackknife in a traffic accident.

Alternative spelling of jack-o'-lantern