a person or thing that kills
a device used by a post office for printing cancellations on postage stamps.
a mark of cancellation made on a postage stamp.
Slang. something or someone having a formidable impact, devastating effect, etc.: The math test was a real killer.
severe; powerful: a killer cold.
very difficult or demanding: a killer chess tournament.
highly effective; superior: a killer recipe for fried chicken.