Knock
WordNet
noun
(1) The act of hitting vigorously
"He gave the table a whack"
(2) Negative criticism
(3) A bad experience
"The school of hard knocks"
(4) The sound of knocking (as on a door or in an engine or bearing)
"The knocking grew louder"
(5) A vigorous blow
"The sudden knock floored him"
"He took a bash right in his face"
"He got a bang on the head"
verb
(6) Find fault with; express criticism of; point out real or perceived flaws
"The paper criticized the new movie"
"Don't knock the food--it's free"
(7) Deliver a sharp blow or push :"He knocked the glass clear across the room"
(8) Knock against with force or violence
"My car bumped into the tree"
(9) Rap with the knuckles
"Knock on the door"
(10) Sound like a car engine that is firing too early
"The car pinged when I put in low-octane gasoline"
"The car pinked when the ignition was too far retarded"
(11) Make light, repeated taps on a surface
"He was tapping his fingers on the table impatiently"
WiktionaryText
Etymology
Akin to Old Norse (compare Danish , to hug) and Middle High German , to hit.
Noun
- An abrupt rapping sound, as from an impact of a hard object against wood
- I heard a knock on my door.
- An impact.
- He took a knock on the head.
- a batsman's innings.
- He played a slow but sure knock of 35.
- A type of abnormal combustion occuring in spark ignition engines. Normally a flame front advances progressively out from the spark, but when knock occurs unburnt air/fuel ahead of the flame self-ignites under the heat and pressure, producing a characteristic knocking sound and a sudden further increase in pressure which can be very damaging to the engine.