Source : Webster's Revised Unabridged Dictionary (1913)

Internecine \In`ter*ne"cine\, a. [L. internecinus deadly,
   murderous, fr. internecare to kill, to slaughter; inter
   between + necare to kill; akin to Gr. ? dead. See
   {Necromancy}.]
   Involving, or accompanied by, mutual slaughter; mutually
   destructive.

         Internecine quarrels, horrible tumults, stain the
         streets with blood.                      --Motley.

Source : WordNet®

internecine
     adj 1: (of conflict) within a group or organization; "an
            internecine feud among proxy holders"
     2: characterized by bloodshed and carnage for both sides;
        "internecine war" [syn: {mutually ruinous}]