OPIOID

I. adjective Date: 1967 possessing some properties characteristic of opiate narcotics but not derived from opium, of, involving, or induced by an ~, II. noun Date: 1967 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, a synthetic drug possessing narcotic properties similar to opiates but not derived from opium