put down

1. An insulting comment with the intention or result of lowering someone's self worth.
   Eg. You stink!
   
   
2. A polite way of saying you're having an animal killed.
   Eg. Really! He was the sweetest pitbull until he brutally attacked your son! We don't want to have to have him put down.
   
   
3. Dropping something from less than an inch or so above where it will land.
   Eg. Put down that knife!

Slang for hitting someone with the intent of knocking them out.

"Shut the fuck up or I'll put you down"

"I'm not joking! One hit and he put the bastard down."

"I'm gonna put him down"