麻痹 has two very different uses: medical (physical paralysis/numbness) and figurative (letting your guard down). The phrase 麻痹大意 (careless and complacent) is extremely common - it means being so relaxed that you forget to be cautious.
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In colloquial/vulgar speech (especially online), 麻痹 or 妈逼 (mābī) is used as a strong expletive. Context makes the meaning clear - the medical/figurative uses are always obvious from surrounding words.
