Opioid

1. A synthetic narcotic that resembles the naturally occurring opiates. 2. Any substance that binds to or otherwise affects the opiate receptors on the surface of the cell.

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Originally, a term denoting synthetic narcotics resembling opiates but increasingly used to refer to both opiates and synthetic narcotics.

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opi·oid 'ō-pē-.ȯid adj

1) possessing some properties characteristic of opiate narcotics but not derived from opium

2) of, involving, or induced by an opioid

opioid n

1) any of a group of endogenous neural polypeptides (as an endorphin or enkephalin) that bind esp. to opiate receptors and mimic some of the pharmacological properties of opiates called also opioid peptide

2) a synthetic drug (as methadone) possessing narcotic properties similar to opiates but not derived from opium broadly opiate (1)

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opi·oid (oґpe-oid) 1. any synthetic narcotic that has opiate-like analgesic activity but is not derived from opium. 2. more broadly, any compound with opiate-like activity. Included here are the opiates; synthetic agents not derived from opium; and naturally occurring peptides that bind at or otherwise influence the opiate receptors of cell membranes, including the dynorphins, endorphins, and enkephalins.