A person who live in the "zone", the area around Chernobyl after its second meltdown. They are illegally there and are bound to no laws. they kill who they want and then suffer the consensuses of that choice. Many are there to get rich off the artifacts and anomalies that where created by the blowouts of the power plant. Others are criminals that have fled there to escape from the law. The Ukrainian and Russian military's are constantly trying to eradicate the S.T.A.L.K.E.R.s but usually have no luck, there are just to many of them and they are under manned.
Pavel- Dude, that guy over there is a S.T.A.L.E.R. he just came out of the zone.
Yakov- I wish I was a S.T.A.L.K.E.R..