No it does not. It just moves your character ~475 in game. However it does counter a few things;
For example, if you flash while blitz has his fist on yoyou, you will not be pulled (Ezreal's arcane shift does this.) If you flash after naut pulls you, it sometimes negates it. If you flash while Naut uses his ultimate as someone like yi with the ability to be very fast, it will fizzle out after 5 seconds.
It will NOT stop autoattacks though, so if you flash on 2 hp with ashe's auto coming at you, chances are you'll die.