What defines a survival horror?

[Hunter of Shadows]

I've been seeing a lot of people completely mislabel some horror games as 'survival horror', when they're not, they're action shooters, yes they have horror elements and can be scary, but if you're playing say like...F.E.A.R which I did see get defined as a survival horror(I couldn't believe it) you play as a dude who goes around blasting with his guns in gun fu style left and right and is such an action hero it's hard to see the game as survival horror.

Especially when the horror elements of FEAR are so...mediocre and unoriginal, so really what I want here is for you people to tell me what you feel defines what survival horror is, I want to understand why people would classify one game as survival horror and one as not.