Originally defining a person from south of "the Mason-Dixon line", can be best used to describe someone who is closed-minded, unwilling to accept others, etc. Also inbred and racist can be used to define a redneck. Usually a fan of "Blue Collar TV" and Jeff Foxworthy. Often says "Y'all".
"Hell, I'm proud to be a red neck. Y'all wanna beer? I got some PBR! Fresh outta the fridge!"