toxic

Etymology

Borrowed from French toxique, from Late Latin toxicus (“poisoned”), from Latin toxicum (“poison”), from Ancient Greek τοξικόν (toxikón) [φάρμακον (phármakon)] ("poison for use on arrows"), from τοξικός (toxikós, “pertaining to arrows or archery”), from τόξον (tóxon, “bow”).

adj

1. (toxicology, pharmacology) Having a chemical nature that is harmful to health or lethal if consumed or otherwise entering into the body in sufficient quantities.
   Tobacco smoke contains many toxic substances.
   If some types of electronic waste aren’t incinerated at a high enough temperature, dioxins, which can cause cancer and developmental problems, infiltrate the food supply. Without proper safeguarding, toxic heavy metals seep into the soil and groundwater. 2019-12-08, Hannah Beech, Ryn Jirenuwat, “The Price of Recycling Old Laptops: Toxic Fumes in Thailand’s Lungs”, in New York Times
2. (medicine) Appearing grossly unwell; characterised by serious, potentially life-threatening compromise in the respiratory, circulatory or other body systems.
   The child appeared toxic on arrival at the hospital.
3. (figurative) Severely negative or harmful.
   a toxic environment that promoted bullying
4. (figurative, of a person) Hateful or strongly antipathetic.
   It is not good to be around toxic people.
   Though Twitter is still overrun with toxic anger and fear-based nonsense (now more than ever), it is also, in one crucial way, beginning to play an important role in our response to the pandemic. 2020-04-23, Cal Newport, “'Expert Twitter' Only Goes So Far. Bring Back Blogs”, in Wired