Definitions
1.VerbTo come to rest, usually briefly, with one of one's knees on the ground.
2.VerbOf any player with the ball, to kneel and place the ball on the ground, thereby ending the play and indicating they do not intend to advance with the ball.
3.VerbTo cease performing customary activities or duties and kneel on one knee, sometimes as a form of protest.
4.VerbUsed other than figuratively or idiomatically: see take, knee."During the play he took a knee to the helmet."