Opioid definition

Opiate.

Designating or of a group of natural or synthetic biochemicals, esp. endorphins, that relieve pain in the same way that opiates do.

Any such biochemical.

Any of various compounds that bind to specific receptors in the central nervous system and have analgesic and narcotic effects, including naturally occurring substances such as morphine; synthetic and semisynthetic drugs such as methadone and oxycodone; and certain peptides produced by the body, such as endorphins.

(pharmacology) Any of a group of synthetic compounds that exhibit similarities to the opium alkaloids that occur in nature.