knock

(noun) the sound of knocking (as on a door or in an engine or bearing). Synonyms: knocking. Example: "The knocking grew louder."

(noun) negative criticism. Synonyms: roast.

(noun) a vigorous blow. Synonyms: bash, bang, smash, belt. Examples: "The sudden knock floored him." "He took a bash right in his face." "He got a bang on the head."

(noun) a bad experience. Example: "The school of hard knocks."

(noun) the act of hitting vigorously. Synonyms: belt, rap, whack, whang. Example: "He gave the table a whack."

(verb) deliver a sharp blow or push :"He knocked the glass clear across the room". Synonyms: strike hard.

(verb) rap with the knuckles. Example: "Knock on the door."

(verb) knock against with force or violence. Synonyms: bump. Example: "My car bumped into the tree."

(verb) make light, repeated taps on a surface. Synonyms: tap, rap, pink. Example: "He was tapping his fingers on the table impatiently."

(verb) sound like a car engine that is firing too early. Synonyms: pink, ping. Examples: "The car pinged when i put in low-octane gasoline." "The car pinked when the ignition was too far retarded."

(verb) find fault with; express criticism of; point out real or perceived flaws. Synonyms: criticize, criticise, pick apart. Examples: "The paper criticized the new movie." "Don't knock the food--it's free."