When a planned event/action/food/etc has a predetermined level of awesomeness which it is expected to reach. If said event/etc reaches this level it is considered to be killer. Surpassing is preferred.

ok so youre going to see a movie right? and you think its going to be really good, and then when you see it it was totally rad.

therefore it was killer.

"this weed is killer"

very cool

That laser light show was killer!

A name given to someone who suddenly becomes over agressive and violent.

Woa slow down killer!

an adjective used to describe high quality thc based substances.

damn, those are some killer thai sticks.

A game you play with a joint or any other marijuana smoking device.
You take a hit and pass it to the next person who does the same, you have to hold in the smoke until the joint gets back to you.
This gets harder if there are more people in the circle
A variation is progressive Killer this is when you increase the amount of hits each time the J goes round the circle

"Yo Niall, rich you up for killer?"
"progressive or normal?"
"progressive man, were hardcore!"

really strong weed. killer weed

man you got any killer
yea yea 10 bucks a g

this killer is killer

A person who kills the flow or vibe of a moment or just messes up the situation by coming in when not wanted or when they say or do something that is unexpected and interrupts the current trend of the moment...usually irritating the people or environment around them.

"This fool killed it by coming to the party."

"I was on the last level of super mario bros and my cousin killed it by stepping on the f'n cable."

"Edgar's new name is killer, because everytime we go out with the ladies this fool has to kill it and scare them away."