adverb
thoroughly or completely
preposition
indicating movement from one side of an opening or location to the other
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He was a dedicated scientist through and through, always committed to his research.
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She's a gamer through and through, you can always find her playing video games.
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He's a skater through and through, he's always shredding at the skate park.
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She's a romantic through and through, always believing in true love.