To flashout is to get highly upset with another person (this may lead to an altercation). Most commonlywhen you flashout on someone it is on a person that you detest.
girl A:(dancing in the club and bumps into girl B)
girl B: Bitch you better watch where you going!
girl A: No you watch where you going!
girl B: Mane, im finna flashout on this hoe!
In the Android custom software users community, someone who is addicted to installing (flashing) new ROMs (customised, unofficial Android versions) or mods every few days.
User: 'Dude, when are you releasing the next version?'
Developer: 'Sorry, flashoholics, haven't got time until next week.'