1. past tense of knuckle; to press or rub with the knuckles
2. past tense of knuckle down; to apply oneself seriously to work or a task
Usage: phrasal verb
3. past tense of knuckle under; to give in or submit to pressure
Usage: phrasal verb

Examples

• She knuckled her tired eyes after staring at the computer screen.
• He knuckled his forehead in frustration.
• The students finally knuckled down and studied for their exams.
• After weeks of procrastination, she knuckled down to finish her project.
• The company knuckled under to union demands.
• He knuckled under the pressure from his boss.
• The massage therapist knuckled the tight muscles in his back.