toxic

American  

[tok-sik] / ˈtɒk sɪk /

adjective

1. of, pertaining to, affected with, or caused by a toxin or poison.

   a toxic condition.

2. acting as or having the effect of a poison; poisonous.

   a toxic drug.

3. causing unpleasant feelings; harmful or malicious: toxic criticism.

   a toxic boyfriend who wanted complete control over her;

   toxic criticism.

4. Finance.

   1. pertaining to or noting debt that will probably not be repaid.

      toxic mortgages.

   2. pertaining to or noting a financial instrument or other asset that has no value or an unknown value because there is no market for it.

      toxic mortgage-backed securities.

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noun

1. a toxic chemical or other substance.

toxic British  

/ ˈtɒksɪk /

adjective

1. of, relating to, or caused by a toxin or poison; poisonous

2. harmful or deadly

3. (of a financial asset) likely to cause significant loss to the holder

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toxic Scientific  

/ tŏk′sĭk /

1. Relating to or caused by a toxin.

2. Capable of causing injury or death, especially by chemical means; poisonous.

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Other Word Forms

• hypertoxic adjective
• nontoxic adjective
• nontoxically adverb
• posttoxic adjective
• toxically adverb
• untoxic adjective
• untoxically adverb

Etymology

Origin of toxic

First recorded in 1655–65; from Late Latin toxicus “poisonous,” derivative of toxicum “poison,” from Greek toxikón (for toxikòn phármakon literally, “bow poison,” i.e., poison used on arrows), equivalent to tóx(on) “bow” + -ikon, neuter of -ikos adjective suffix; see -ic

Explanation

Danger! Hazardous! Do not eat! These are just some of the warnings you'll see on toxic substances — meaning stuff that's poisonous and even deadly. Cobra bites, wild mystery mushrooms and strong chemicals are all toxic. So are certain people, if they have particularly mean personalities. Toxic is related to the word toxin, which is a kind of poison. It comes from the ancient Greek word toxikon, which means "poison for arrows." Some toxic arrows could come in handy for those toxic personalities...

Example Sentences

The industry has been under pressure to find alternatives because sulfuryl fluoride, the chemical used in fumigation, is toxic to humans and also acts as a greenhouse gas.

From Science Daily • Apr. 20, 2026

Comparisons can be drawn with Leicester and Southampton last season, Wolves initially shared that toxic cloud earlier this season which has, in the Foxes' case, failed to lift.

From BBC • Apr. 20, 2026

Another concern is consumers—especially those “stacking” or taking multiple peptides—who may face long-term toxic effects, says Knoepfler.

From The Wall Street Journal • Apr. 20, 2026

“And that creates this really toxic reinforcement loop.”

From MarketWatch • Apr. 17, 2026

She didn’t look like she’d just fallen into toxic sludge.

From "The First Rule of Punk" by Celia C. Pérez

Related Words

• deadly
• harmful
• lethal
• noxious
• pernicious
• virulent