cutthroat

Concise Oxford English Dictionary © 2008 Oxford University Press:
cut-throat

▶noun

• 1 dated a murderer or other violent criminal.

• 2 (also cut-throat trout) a trout of western North America, with red or orange markings under the jaw. [Salmo clarki.]

▶adjective

• 1 ruthless and intense: cut-throat competition.

• 2 (of some card games) played by three rather than four players.