opioid

noun Biochemistry, Pharmacology.

1. any opiumlike substance.
2. any of a group of natural substances, as the endorphins, produced by the body in increased amounts in response to stress and pain.
3. any of several synthetic compounds, as methadone, having effects similar to natural opium alkaloids and their derivatives.

adjective

4. pertaining to such a substance.

noun

1. 1. any of a group of substances that resemble morphine in their physiological or pharmacological effects, esp in their pain-relieving properties
   2. (modifier)of or relating to such substancesopioid receptor; opioid analgesic

n.1957, from opium + -oid. n.

1. opiate

adj.

1. Opiate.