Definition of friendly fire
: the firing of weapons from one's own forces or those of an ally especially when resulting in the accidental death or injury of one's own personnel <Near the river bordering our camp I find the tents of the four soldiers who were supposedly hit by friendly fire. — Janine Di Giovanni> <After all, accidental attacks, though tragic, are common in war. In 1967 alone, “friendly fire” killed 5,373 Americans fighting in Vietnam. — Michael Oren>
First Known Use of friendly fire
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