Toxic means poisonous — able to cause serious harm if swallowed, breathed or absorbed. Toxic chemicals, toxic fumes, highly toxic.
It is the technical word: toxic waste, toxicology, non-toxic on a label. The figurative sense has spread very fast and is now at least as common — a toxic workplace, a toxic relationship, toxic positivity — meaning harmful to be around. In finance, a toxic asset is one nobody can value or sell. Note toxin, which is a poison produced by a living thing, and is not simply any toxic substance.
1adjectivetoxicPoisonous; able to cause serious harm.
“The fumes are toxic in a closed room.”
synonyms: poisonous, noxious
2adjectiveharmfulHarmful to be around.
“The atmosphere in that office was toxic by the end.”
toxic is a quality of being harmful.
Also accepted in games: poisonous
Greek toxikon was the poison smeared on arrows, from toxon, a bow. The word for poison in English therefore descends from archery equipment, by way of the phrase for what was painted on the arrowheads.
French
toxique
English, today
toxic
Built from
Borrowed from French toxique. Borrowed from French toxique, from Latin toxicus (“poisoned”), from Latin toxicum (“poison”), from Ancient Greek τοξικόν [φάρμακον] ("poison for use on arrows"), from τοξικός (“pertaining to arrows or archery”), from τόξον (“bow”).
Etymology from Wiktionary, CC BY-SA