Ruthlessly competitive with no regard for fairness; or a person who is ruthless and willing to harm others for profit.
From 'cut' + 'throat,' a compound literally describing one who cuts throats. The phrase became metaphorical for ruthless competition, especially in business during the 1800s when markets were brutal.
Cutthroat trout fish are named after the red slash marks under their throats that look like a cut—so the metaphor actually works backwards: humans adopted a ruthless term that was literally visible on a fish, showing how nature's vocabulary bleeds into human language.
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