Definition:
"Killer" is a slang term used to describe something or someone that is really cool, impressive or amazing.
Use case:
You can use "killer" to describe a variety of things such as a great song, a fantastic meal, a stunning view, an impressive performance, or a person who is exceptionally talented or attractive. For example, "That new restaurant downtown has killer food!" or "Did you see that killer guitar solo during the concert?"
• This pizza is killer - I'm definitely ordering from this place again.
• That skateboarding trick was killer - you could win the competition with moves like that.
• The killer party last night had me feeling like a rockstar all evening.
• The new horror movie I watched last night was so killer, I couldn't sleep until dawn.
• Your new haircut looks killer - it suits you so well!
• My new workout routine is absolutely killer - I can barely move today!