friendly fire

noun

1. Insurance. a fire deliberately set and remaining contained, as in a fireplace or boiler, from which any resulting loss cannot be claimed as an insurance liability (opposed to hostile fire).
2. (in military combat) fire, as by artillery, by one’s own forces, especially when causing damage near or casualties to one’s own troops.

noun

1. military firing by one’s own side, esp when it harms one’s own personnel