A person or thing that defeats another; one who wins against an opponent or overcomes an obstacle.
From defeat + -er (agent noun). This straightforward agent noun has been used in English for centuries to name the person or force causing defeat.
In medieval tournament records, 'defeaters' were celebrated in poetry and became legendary—defeating a famous knight was the path to glory. Today the word is mundane, but it once carried enormous prestige and power in describing people.
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