knock

noun

Sudden fatigue as a result of glycogen depletion from not having taken in enough nutrition.

1. An abrupt rapping sound, as from an impact of a hard object against wood.

   I heard a knock on my door.

2. A sharp impact.

   He took a knock on the head.

3. Criticism.
4. Preignition, a type of abnormal combustion occurring in spark ignition engines caused by self-ignition; also, the characteristic knocking sound associated with it.
5. A batsman's innings.

   He played a slow but sure knock of 35.

1. To strike for admittance; to rap upon, as a door.
2. To criticize verbally; to denigrate; to undervalue.

   Don’t knock it until you’ve tried it.

3. To kick a ball towards another player; to pass.
4. To impress forcibly or strongly; to astonish; to move to admiration or applause.
5. To bump or impact.

   I accidentally knocked my drink off the bar.

6. To rap one's knuckles against something, especially wood.

   Knock on the door and find out if they’re home.