From time to time you may hear English speakers use the word killer in a sense that has nothing to do with killing something!
Killer can be used as an adjective to describe something that is very good, excellent or even hard.
"That was a killer game of football" = It was a very good game of football.
"That was a killer exam" = It was a very hard exam.
Killer can be used as a noun, in the form of a greeting that suggests the person being greeted in a very cool person.
"Hey Killer, how are you today?"
Remember unless you are 100% sure of English and English slang, we recommend you don't use it as if used wrongly it may cause great offence.
However we do recommend that you learn slang so that when you hear it, you understand it.
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