noun
One who or that which kills.
There’s a killer on the loose.
My cat is a habitual bird killer.
That which causes stress or is extremely difficult, especially that which may cause failure at a task.
That test was a killer.
The final hill in the race course was a killer.
Something that is so far ahead of its competition that it effectively kills off that competition.
Digital streaming platforms are CD killers.
A remarkably impressive person or thing.
Picture perfect, you don't need no filter / Gorgeous, make 'em drop dead, you're a killer
A knockout form of darts or pool involving several players.
adj
Excellent, very good, cool.
killer feature
killer view
Causing death, destruction, or obliteration.
killer bee
killer robot
Distressing, uncomfortable.
I had a killer headache this morning.