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

In Long Bright River, now streaming on Peacock, Seyfried plays Mickey, a police officer who works in the Philadelphia neighborhood of Kensington at the height of the opioid crisis. —Carly Tagen-Dye, People.com, 14 Mar. 2025

Writing in Nature developmental psychologist Candice Odgers suggests that broader societal challenges, including violence and the opioid crisis, may have a more significant impact on teen well-being. —Rob Morris, Forbes, 14 Mar. 2025

Adjective

The number of prescriptions issued for medical marijuana in Poland increased sixfold recently, along with a rise in prescriptions for opioid medications. —Tribune Content Agency, The Mercury News, 13 Mar. 2025

About half those prescriptions are written for opioid medications, which can lead to dependence and addiction. —CNN, 3 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