Knock around (2) INFORMAL
If you knock around with someone, you spend time together because you're friends.
Knock back (1) INFORMAL
to take a drink, usually alcoholic
Knock back (2) INFORMAL
to reject someone or something or to refuse a request for something
knock down (1)
If something like a building or a wall is knocked down, it is destroyed on purpose.
knock down (2) 
to hit someone with a vehicle
Knock off (1) INFORMAL
to stop work for the day
Knock off (2) INFORMAL
to steal something
Knock off (3) INFORMAL
to murder somebody
Knock off (4) INFORMAL
to reduce something, like a price or an amount
knock out (1)
If you are knocked out, you are hit so hard that you lose consciousness.
Knock out (2) INFORMAL
If you knock somebody out, you impress them very much with something you do, or something you make.
knock out (3)
If you knock somebody out of a competition, they cannot continue because you've defeated them.
knock over (1)
to hit somebody with a vehicle and injure or kill them
Knock over (2) INFORMAL
to rob something like a bank or a shop