Meaning

noun someone who uses another person's words or ideas as if they were his own

noun someone who robs at sea or plunders the land from the sea without having a commission from any sovereign nation

noun a ship that is manned by pirates

originFrom Middle English pirate, pirat, pyrat, from Old French pirate, from Latin pīrāta (“pirate”), from Ancient Greek πειρατής (peiratḗs), from πεῖρα (peîra, “trial, attempt, plot”). Displaced native Old English wīċing, which was the word for both "pirate" and "viking".

Etymology from Wiktionary, CC BY-SA 3.0