Wiktionary
n. The hook that develops in the lower jaw of an adult male salmon when it is ready to spawn.
Wikipedia
A kype is a hook-like secondary sex characteristic which develops at the distal tip of the lower jaw in some male salmonids prior to the spawning season. The structure usually develops in the weeks prior to, and during, migration to the spawning grounds. In addition to the development of the kype, a large depression forms in the two halves of the premaxilla in the upper jaw, allowing the kype to fit into the premaxilla when the mouth is closed.
The kype functions as a secondary sexual characteristic and influences the formation of dominance hierarchies at the spawning grounds. The size of the kype is believed to determine male spawning frequency.
Usage examples of "kype".
The paint had been kyped from the county equipment yard the year before.
Anna, and leaving South Beveland behind them turned up the channel called the Kype, between the Islands of North Beveland and Duveland.