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.

simple past tense and past participle of jack-knife

Third-person singular simple present indicative form of jack-knife

present participle of jack-knife

An unlicensed performer of abortions; backstreet abortionist

plural of jack-knife barber