It's a 'torch' in British English. The word 'flashlight', until recently, would have suggested something that flashed on and off to give a signal. However, US-led globalisation of language is unstoppable, and 'flashlight' is becoming more common in Britain and worldwide. The nifty little phone app that turns your mobile into a torch, for example, is called 'flashlight'. And the more young people who see and use this term, the more it is absorbed into the language.