opioid

1 of 2

noun

opi·​oid ˈō-pē-ˌȯid 

plural opioids

: a natural, semisynthetic, or synthetic substance that typically binds to the same cell receptors as opium and produces similar narcotic effects (such as sedation, pain relief, slowed breathing, and euphoria):

a

or less commonly opioid peptide : any of various of endogenous polypeptides (such as an endorphin or enkephalin) produced by neurons of the peripheral and central nervous system

The people who rated pain the lowest were those whose brains began producing natural painkillers called opioids the fastest …

—John O'Neil

b

: any of various opiates (such as morphine), semisynthetic opiate derivatives (such as heroin, hydrocodone, or oxycodone), or synthetic preparations (such as fentanyl or methadone) that may be used illicitly for their narcotic properties and are associated with physiological tolerance (see tolerance sense 4a(1)), physical and psychological dependence, or addiction upon repeated or prolonged use

… fentanyl, a synthetic opioid at least 75 times more potent than morphine.

—Ryan Trimble and Eric S. Peterson

Naltrexone is an opioid antagonist used for the treatment of heroin addiction.

—Scientific American

The prototypical opioids are morphine and codeine (which is milder than morphine).

—Harvard Health Letter

When Walker County was identified as the epicenter of Alabama's opioid crisis, it was no surprise to residents who watched as drugs brought death and devastation down upon their families, neighbors and communities.

—Ashley Remkus

Note: The word opioid was originally used only for morphine-like substances not derived from opium, but it has now become widely accepted as a broader term encompassing any substance—natural or synthetic, opium-derived or not—that binds to opiate cell receptors and induces sedation, analgesia, and euphoria.

opioid

2 of 2

adjective

: possessing narcotic properties characteristic of opiates : of, relating to, involving, or being an opioid

opioid drugs

opioid addiction

endogenous opioid endorphins

opioid cell receptors

Examples of opioid in a Sentence

Recent Examples on the Web

Noun

On that note, lorazepam can also interact with other medications that depress the central nervous system, like opioids, antipsychotics, antidepressants, anticonvulsants, certain antihistamines, and more. —Korin Miller, SELF, 3 Mar. 2025

During her visit to Johns Hopkins, the hospital conducted a screening of her blood for fentanyl as part of a routine policy; at the time, the protocol was to test all patients for the synthetic opioid because of a spike in overdose cases at the Baltimore medical center. —Jay Weaver, Miami Herald, 28 Feb. 2025

Adjective

And more people are benefitting from policies to expand access to treatments like methadone and buprenorphine which reduce opioid cravings and withdrawal symptoms, while cutting overdose risk in half. —Thomas G. Moukawsher, Newsweek, 4 Mar. 2025

Housing is the solution, Kushel said, but until enough of it is available, there is a need to bring more resources to the street, such as methadone or other medications that treat opioid addiction. —Doug Smith, Los Angeles Times, 27 Feb. 2025

Word History

Etymology

Noun

opium + -oid entry 1

Adjective

opium + -oid entry 2

First Known Use

Noun

1957, in the meaning defined above

Adjective

1967, in the meaning defined above

Phrases Containing opioid

• opioid peptide

Rhymes for opioid

• adenoid
• alkaloid
• amoeboid
• amyloid
• aneroid
• anthropoid
• arachnoid
• asteroid
• benzenoid
• carcinoid
• celluloid
• coronoid

Kids Definition

opioid

noun

opi·​oid ˈō-pē-ˌȯid 

: any substance that binds to the same cell receptors as opium, produces similar effects (as sleepiness and pain relief), includes drugs used medically especially as painkillers, is often used illicitly for its narcotic properties, and often causes physical and psychological dependence

Medical Definition

opioid

1 of 2 noun

ˈō-pē-ˌȯid 

: a natural, semisynthetic, or synthetic substance that typically binds to the same cell receptors as opium and produces similar narcotic effects (such as sedation, pain relief, slowed breathing, and euphoria):

a

also opioid peptide : any of various of endogenous polypeptides (such as an endorphin or enkephalin) produced by neurons of the peripheral and central nervous system

b

: any of various opiates (such as morphine), semisynthetic opiate derivatives (such as heroin, hydrocodone, or oxycodone), or synthetic preparations (such as fentanyl or methadone) that may be used illicitly for their narcotic properties and are associated with physiological tolerance (see tolerance sense 1), physical and psychological dependence, or addiction upon repeated or prolonged use

… fentanyl, a synthetic opioid at least 75 times more potent than morphine.

—Ryan Trimble and Eric S. Peterson

The prototypical opioids are morphine and codeine (which is milder than morphine).

—Harvard Health Letter

Note: The word opioid was originally used only for morphine-like substances not derived from opium, but it has now become widely accepted as a broader term encompassing any substance—natural or synthetic, opium-derived or not—that binds to opiate cell receptors and induces sedation, analgesia, and euphoria.

opioid

2 of 2 adjective

opi·​oid

: possessing narcotic properties characteristic of opiates : of, relating to, involving, or being an opioid

opioid drugs

opioid addiction

endogenous opioid endorphins

opioid cell receptors