Pronunciation: (kil'ur), [key]
1. a person or thing that kills.
2. See killer whale.
3. a device used by a post office for printing cancellations on postage stamps.
4. a mark of cancellation made on a postage stamp.
5. Slang.something or someone having a formidable impact, devastating effect, etc.: The math test was a real killer.
severe; powerful: a killer cold.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.