rivalry, competition, conflict, and disagreement between the members of a group, often bitter and not engaged in publicly, and often continuing over a period of time;
e.g. Their progress was hindered by infighting, since they were distracted by their own internal quarrels.
(noun)
boxing or some other form of hand-to-hand combat, when engaged in at close quarters, nearer than an arm's length to one's opponent;
e.g. Towards the end of a bout, players may switch to infighting and become more aggressive.