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

toxics plural

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

Derived Forms

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

Inflected Forms

Nouns

• toxics
  plural

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

Toxic air has covered the San Gabriel Valley and beyond at times, as the fire continues to burn and the wind shifts the pall in different directions.

From Los Angeles Times • Jun. 23, 2026

Appeared in the June 5, 2026, print edition as 'Milei’s Online Combativeness Turns Toxic'.

From The Wall Street Journal • Jun. 5, 2026

Short-term exposure to EtO by inhalation can cause headaches, dizziness, nausea, fatigue respiratory irritation and other adverse health effects, according to the federal Agency for Toxic Substances and Disease Registry.

From Los Angeles Times • May 14, 2026

The "Toxic" singer was arrested in March after police spotted her driving erratically on a freeway in Ventura County, near Los Angeles.

From Barron's • May 4, 2026

“You have to tell your emotional truth,” says Susan Forward, a therapist and the best-selling author of Toxic Parents.

From "A Deadly Wandering: A Mystery, a Landmark Investigation, and the Astonishing Science of Attention in the Digital Age" by Matt Richtel

Related Words

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