Medical Definition of opium
: a highly addictive drug that consists of the dried milky juice from the seed capsules of the opium poppy obtained from incisions made in the unripe capsules of the plant, that has a brownish yellow color, a faint smell, and a bitter and acrid taste, that is a stimulant narcotic usually producing a feeling of well-being, hallucinations, and drowsiness terminating in coma or death if the dose is excessive, that was formerly used in medicine to soothe pain but is now often replaced by derivative alkaloids (as morphine or codeine) or synthetic substitutes, and that is smoked illicitly as an intoxicant with harmful effects
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