1. plural of jackknife; folding pocket knives with blades that fold into the handle

1. third person singular present of jackknife; folds sharply at an angle like a closing jackknife
2. performs a diving position where the body bends at the waist with legs straight
Usage: diving

Examples

• He carries two jackknives in his camping gear.
• The old fisherman’s jackknives were well-worn from years of use.
• The truck jackknives on the icy highway during the storm.
• She jackknives into the pool with perfect form.
• The trailer jackknives when the driver brakes too hard.
• He jackknives off the diving board at the competition.
• The swimmer jackknives gracefully before entering the water.