a person who takes something that belongs to someone else without permission; a thief.
From Old English 'stelan' (to steal) plus the agent suffix '-er' (one who does something). The concept of stealing is ancient, appearing in English legal documents and moral codes dating back over a thousand years.
In basketball, a 'steal' is actually a good thing—it means you took the ball from the other team! But everywhere else, being called a 'stealer' is definitely an insult. Language is context-dependent.
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