To discharge waste material from the bowels; to have a bowel movement.
From Latin 'defaecate' (de- away + faecere from faeces meaning dregs/waste). The term was originally used in chemistry for removing impurities before becoming the standard medical term.
The word started in chemistry labs where it meant 'to remove feces' or impurities from liquids—doctors borrowed it for the human biological process because it's a polite, scientific-sounding term instead of crude slang.
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