Definitions

1. noun

a folding pocket knife, typically having a blade that can be opened and closed with one hand, often carried by truck drivers.

“The truck driver pulled out his jackknife to change the tire.”

2. verb

to cut or sever something with a swift, sharp motion, especially a knife.

“She jackknifed the rope to release the tension.”

3. verb

to swerve or turn sharply, especially in a sudden or unexpected manner.

“The car jackknifed on the icy road, causing a major accident.”