knock

from The American Heritage® Dictionary of the English Language, 5th Edition.

• intransitive verb To strike with a hard blow.
• intransitive verb To affect in a specified way by striking hard.
• intransitive verb To cause to be displaced or unengaged; force.
• intransitive verb To cause to collide.
• intransitive verb To produce by hitting or striking.
• intransitive verb Informal To find fault with; criticize.
• intransitive verb To strike a sharp audible blow or series of blows, as on a door.
• intransitive verb To collide with something.
• intransitive verb To make a pounding or clanking noise.
• noun An instance of striking or colliding.
• noun The sound of a sharp blow on a hard surface.
• noun A pounding or clanking noise made by an engine, often as a result of faulty fuel combustion.
• noun Slang A cutting, often petty criticism.
• idiom (have it knocked) To be certain of success.
• idiom (knock cold) To render unconscious; knock out.
• idiom (knock dead) To kill with a blow.
• idiom Slang (knock dead) To affect strongly and positively.
• idiom (knock it off) To stop doing something. Often used in the imperative.
• idiom (knock out of the box) To force the removal of (an opposing pitcher) by heavy hitting.
• idiom (knock (someone's) socks off) To overwhelm or amaze.
• idiom (knock some sense into) To beat or hit (someone) in an effort to teach a lesson or cause a person to adopt an acceptable pattern of behavior.

from The Century Dictionary.

• noun A blow; a buffet; a stroke with the fist, or with anything hard or heavy, as a cudgel, a hammer, or the knocker of a door.