Definition of "toxic"

toxic

/ˈtɒk.sɪk/

adjective
comparative more toxic, superlative most toxic
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.
  Quotations
  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 December 8, 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.
3. (figurative) Severely negative or harmful.
4. (figurative, of a person) Hateful or strongly antipathetic.
  Quotations
  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 April 23, Cal Newport, “'Expert Twitter' Only Goes So Far. Bring Back Blogs”, in Wired‎