The most notorious or chief pirate; a leader of pirates or one considered the worst of all pirates.
From arch- (meaning chief or principal, from Greek arkhē) combined with pirate (from Greek peiratēs, one who attempts or attacks). The prefix arch- has been used since Middle English to denote the supreme example of something.
Medieval and early modern writers loved stacking 'arch-' prefixes to describe villains and heroes—it's like calling someone the 'ultimate' version of their role. Blackbeard was sometimes called an 'archpirate' because he was so famously ruthless.
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