- any of a group of substances that resemble morphine in their physiological or pharmacological effects, esp in their pain-relieving properties
WordReference Random House Unabridged Dictionary of American English © 2017
- Physiology, Biochemistry, Drugsany opiumlike substance.
- Physiology, Biochemistry, Drugsany of a group of natural substances, as the endorphins, produced by the body in increased amounts in response to stress and pain.
- Biochemistry, Drugsany of several synthetic compounds, as methadone, having effects similar to natural opium alkaloids and their derivatives.
- Physiology, Biochemistry, Drugspertaining to such a substance.
- opi(um) + -oid 1955–60