From Longman Dictionary of Contemporary Englishflashgunflash‧gun /ˈflæʃɡʌn/ noun [countable] TCPa piece of equipment that lights a special bright light when you press the button on a camera to take a photograph
Examples from the Corpus
flashgun• In photography, even if you buy a Leica, you buy a flashgun from some one else.• Perhaps he had been caught unawares by a flashgun?• Imagine that we stand beside the track with a flashgun.• I purchased a dedicated Pentax flashgun with an adjustable flash head which could be adjusted to point straight ahead or angled upwards. 