1
general::
Render extinct, eliminate completely, as in The plague killed off entire villages and towns. [c. 1600] 1. Represent as dead, as in This mystery writer kills off a new victim in almost every chapter. [Mid1800s] 2.
American Heritage Idioms
2
general::
Phrase(s): kill someone or an animal off
to kill all of a group of people or creatures. • Lefty set out to kill Max and his boys off. • Something killed off all the dinosaurs.
McGrawhill's American Idioms And Phrasal Verbs