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.
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

British Dictionary definitions for friendly fire

friendly fire

noun
  1. military firing by one's own side, esp when it harms one's own personnel
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012