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: Don't knock the weather; nine-tenths of the people couldn't start a conversation if it didn't change once in a while.
Whack
Part of speech: noun
Definition: A blow, impact or slap.A share or portion.An attempt.
Part of speech: verb
Definition: To hit, slap or strike.To kill, bump off.To share or parcel out.
Example sentence: With epic fantasy, there is a tendency for it to be quintessentially conservative in that its job is to restore what is perceived to be out of whack.