This abbreviation stands for "knuckle dragging retard" the definition of this term is a blue collar worker who's upper management looks down upon them simply because he/she was born without the same money and opportunities they were born into. So the managers condescend to the mechanic even when the mechanic provides correct and/or better solutions to the problem.
"That knuckle dragging retard thinks he knows better than I do! He found eight spices arcing in my wing strobe light wiring and tells me it only needs new wire ran! I told him to change the power supply, not the wire, and then get back to flinging boogers for team KDR!!"
KDR literally translates to Gae kid born to a woman with a penis and a man with vagina. The kid grows up to like fembois and traps
He is such a KDR.
Someone you call who is brown/Dark skinned and attractive