The
Kill Death Ratio, Commonly Referred to as K/D, KDR or
Kill/Death, is the average rate of the amounts of deaths you need per
kill. For instance, a KDR of 1 means that your number of death equals the number of kills you have. If your KDR is lower than one, then you have more deaths than kills, and vice versa.
Summary (may require some mathematical understanding):
If 0 < k < 1, or log(k) < 0, then you are a
n00b.
If k > 1, or log(k) > 0, then you are a good player.
(k is your Kill Death Ratio)