I. ˈōpēˌȯid adjective
Etymology: opi ate (II) + -oid
1. : possessing some properties characteristic of opiate narcotics but not derived from opium
2. : of, involving, or induced by an opioid
II. noun
( -s )
1. or opioid peptide : any of a group of endogenous neural polypeptides (as an endorphin or enkephalin) that bind especially to opiate receptors and mimic some of the pharmacological properties of opiates
2. : a synthetic drug that possesses narcotic properties similar to opiates but is not derived from opium ; broadly : opiate 1