means The scientific study of poisons — how toxic substances affect living things, at what doses they harm, and how to detect, prevent, or treat that harm.

from From Greek 'toxikon,' poison — but the word hides an archer. 'Toxikon' was short for 'toxikon pharmakon,' the 'poison for the bow,' from 'toxon,' a bow. So the venom smeared on arrowheads gave its name to the entire study of poisons, joined to '-logia,' the study of. Toxicology is, quite literally, the science of what's on the arrow.