Typically a redneck term depicting an African American in an unflattering manner. KG is short for the first letters of the two words "Knee and Grow", an alternate spin on the spelling of the word "negro".
"Hey Brian check out that filthy KG looking to buy that property next door, that sure going kill our property values."
"Glen was going to pick up some wings at KFC, but ended up going for pizza instead because the KFC was full of cunnerman and KG's"
"Paige, why can't you ever date someone other than a KG, there are plenty of white guys around"