■ noun Geology the boundary between the Cretaceous and Tertiary periods, about 65 million years ago, marked by the extinction of dinosaurs and many other groups of animals.
Origin
from symbols for Cretaceous and Tertiary .
K/T BOUNDARY
Meaning of K/T BOUNDARY in English
Concise Oxford English vocab. Сжатый оксфордский словарь английского языка. 2004