/ ˌɪntəˈniːsaɪn; NAmE -tərˈn-/ adjective
[ only before noun ] ( formal ) happening between members of the same group, country or organization :
internecine struggles / warfare / feuds
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WORD ORIGIN
mid 17th cent. (in the sense deadly, characterized by great slaughter ): from Latin internecinus , based on inter- among + necare to kill.