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

Testing from the Department of Toxic Substance Control found no radiation levels above background and no hazardous compound levels other than those normally present after a wildfire.

From Los Angeles Times • May 22, 2026

The intended target was said to have been a rapper called Trapstar Toxic, real name Adetokunbo Ajibola, 33, who was at the event, the court heard.

From BBC • May 20, 2026

Toxic amounts of cobalt and aluminum saturated the earth, poisoning the plants.

From "The Science of Breakable Things" by Tae Keller

Related Words

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