(n) The root of the word "derogatory." When applied to a person it indicates simply that the speaker wishes to insult that person. Its nice, hard consonents at either end, and the fact that it has no specific meaning add to the impact of the insult. Takes adjectives well.
Used similarly to "bastard" when that word is not used to refer to a person's parentage.
You're a filthy, stinking derog.