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

Experts attribute the decrease to a combination of factors, including the wider availability of the opioid antidote naloxone, along with $50 billion in funding for drug-treatment and youth prevention efforts from the national opioid settlements. —Adrianna Rodriguez, USA Today, 15 May 2025

What To Know The CDC said drug overdose deaths were down 27 percent from 110,000 in 2023, and put this in part down to Trump declaring the opioid crisis a public health emergency during his first term in 2017. —Dan Gooding, MSNBC Newsweek, 14 May 2025

Adjective

At Wednesday’s hearing, before the House Appropriations Committee, Representative Madeleine Dean, Democrat of Pennsylvania, whose son is in recovery from opioid addiction, took Mr. Kennedy to task, noting his own history of heroin addiction. —Jan Hoffman, New York Times, 15 May 2025

The drug is often taken recreationally, though if stopped abruptly, users could experience withdrawal symptoms similar to those associated with opioid withdrawal – craving, sweating, diarrhea and more. —Greg Wehner, FOXNews.com, 12 May 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