Knock
Part of speech: noun
Definition: An abrupt rapping sound, as from an impact of a hard object against wood An impact. a batsman's innings. 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.
Part of speech: verb
Definition: To rap one's knuckles against something, especially wood. To bump or impact. To denigrate, undervalue.
Example sentence: Americans knock themselves out, especially since 9/11, praising the military.
Knocking
Part of speech: verb
Definition: To strike for admittance; to rap upon, as a door.
Part of speech: noun
Definition: An act in which something is knocked on, or the sound thus produced
Example sentence: When people think of me, they think about me knocking catchers down and knocking second basemen down and yelling at pitchers. But when I took the spikes off after the game, I was a nice guy when I went home.