knock

(noun): Sudden fatigue as a result of glycogen depletion from not having taken in enough nutrition.
(noun): An abrupt rapping sound, as from an impact of a hard object against wood.
(noun): A sharp impact.
(noun): Criticism.
(noun): Preignition, a type of abnormal combustion occurring in spark ignition engines caused by self-ignition; also, the characteristic knocking sound associated with it.
(noun): A batsman's innings.
(verb): To strike for admittance; to rap upon, as a door.
(verb): To criticize verbally; to denigrate; to undervalue.
(verb): To kick a ball towards another player; to pass.
(verb): To impress forcibly or strongly; to astonish; to move to admiration or applause.
(verb): To bump or impact.
(verb): To rap one's knuckles against something, especially wood.