Douglas Harper's Etymology Dictionary
WordNet
n. conflict between members of the same organization (usually concealed from outsiders)
boxing at close quarters
Usage examples of "in-fighting".
I even engaged in corporate in-fighting, preventing the transfer of the catfood company from my division to General Foods.
There were installed the Italian customs of levying taxes in order to raise money for substantial bribes, of hatching plots and machinations of labyrinthine complexity, of arranging catastrophically inappropriate marriages of convenience, of merciless in-fighting, of family feuding, of swapping the island between one Italian despotate and another (so that for a while we were part of Naples), and finally, in the eighteenth century there was such a prodigious outbreak of violence between the leading families (the Aninos, Metaxas, Karoussos, Antypas, Typaldos, and Laverdos) that the authorities deported all the agitators to Venice and hanged them.
For several weeks Bless headed a special detail to train people recruited from the free political parties, the free union, and the Western Sector students in the tricks of in-fighting, riot control, and all of the brawling tactics known to the Communist Action Squads- plus a few of Bless's own innovations.