Webster's Revised Unabridged Dictionary · 1913

Internecine

Internecine , adjective

[Latin internecinus deadly, murderous, from internecare to kill, to slaughter; inter between + necare to kill; akin to Greek {not transcribed} dead. See Necromancy.]

1.
Involving, or accompanied by, mutual slaughter; mutually destructive.
Internecine quarrels, horrible tumults, stain the streets with blood. — Motley
2.
Of or pertaining to internal conflicts within a group; as, internecine quarrels.