knock

Etymology

From Middle English knokken, from Old English cnocian, ġecnocian, cnucian (“to knock, pound on, beat”), from Proto-West Germanic *knokōn, from Proto-Germanic *knukōną (“to knock”), a suffixed form of *knu-, *knew- (“to pound on, beat”), from Proto-Indo-European *gnew-, *gen- (“to squeeze, pinch, kink, ball up, concentrate”). The English word is cognate with Middle High German knochen (“to hit”), Old English cnuian, cnuwian (“to pound, knock”), Old Norse knoka (compare Danish knuge (“to squeeze”), Swedish knocka (“to hug”)).

noun

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. (figurative) A criticism.
   Since forming in 2007 Mumford & Sons have hard-toured their way to a vast market for throaty folk that's strong on banjo and bass drum. They have released two enormous albums. But, wow, do they take some knocks back home. 15 November 2012, Tom Lamont, The Daily Telegraph
4. (figurative) A blow or setback.
   "Come on!" cried Mr. Beaver, who was almost dancing with delight. "Come and see! This is a nasty knock for the Witch! It looks as if her power was already crumbling." 1950, C. S. Lewis, The Lion, the Witch and the Wardrobe
5. (automotive, uncountable) Preignition, a type of abnormal combustion occurring in spark ignition engines caused by self-ignition; also, the characteristic knocking sound associated with it.
6. (cricket) A batsman's innings.
   He played a slow but sure knock of 35.
7. (cycling, uncountable) Synonym of hunger knock

verb

1. (intransitive) To rap one's knuckles against something, especially wood.
   Knock on the door and find out if they’re home.
2. (transitive, dated) To strike for admittance; to rap upon, as a door.
3. (transitive, colloquial, originally US) To criticize verbally; to denigrate; to undervalue.
   Don’t knock it till you’ve tried it.
   A Judge must be respected, / A Judge you mustn't knock / Or else you'll be detected / And shoved into the dock. 1918, Norman Lindsay, The Magic Pudding, page 148
   And what do you care when some folks start knocking you? It’s a sign you getting some place. 1952, Ralph Ellison, Invisible Man, Penguin Books, published 2014, page 386
   The pious have sometimes knocked the day [Thanksgiving] for its laughter, its late sleeping, its overeating. 1980-11-27, “Inclusive”, in The New York Times, →ISSN
4. (transitive, soccer) To kick a ball towards another player; to pass.
   Despite enjoying more than their fair share of possession the visitors did not look like creating anything, with their lack of a killer ball painfully obvious as they harmlessly knocked the ball around outside the home side's box without ever looking like they would hurt them. 11 January 2011, Jonathan Stevenson, “West Ham 2 – 1 Birmingham”, in BBC Sport
5. (transitive, Britain, slang, dated) To impress forcibly or strongly; to astonish; to move to admiration or applause.
6. (transitive, intransitive, dated) To bump or impact.
   I knocked against the table and bruised my leg.
   I accidentally knocked my drink off the bar.
7. (transitive, slang) To have sex with.
8. (transitive, slang) To prosecute under the law; to arrest, imprison, etc.