1 : marked by slaughter : deadly; especially : mutually destructive
*2 : of, relating to, or involving conflict within a group
When Pinky put the two peanuts together , it didn't take long for the internecine feuding to begin.
Did you know?
"Internecine" comes from the Latin "internecinus" ("fought to the death" or "destructive"), which traces to the verb "necare" ("to kill") and the prefix "inter-." ("Inter-" usually means "between" or "mutual" in Latin, but it can also indicate the completion of an action.) "Internecine" meant "deadly" when it appeared in English in 1663, but when Samuel Johnson entered it in his dictionary almost a century later, he was apparently misled by "inter-" and defined the word as "endeavouring mutual destruction." Johnson's definition was carried into later dictionaries, and before long his sen se was the dominant meaning of the word. "Internecine" developed the association with internal group conflict in the 20th century, and that's the most common sense today.
*Indicates the sense illustrated in the example sentence.