As the fates would have it, found this applicable little essay. I was kind of (okay totally) out of control this week, a regular jerkette. Just ask Kenzie and ld. I even went so far as to pinch ld's sore nipple, I was just that angry and frustrated. It didn't help that they both laughed at my craziness.
Thinking it over, I decided that a jerk is basically a person without insight. He is not necessarily a fool or a dope, because some extremely clever persons can be jerks. In fact, it has little to do with intelligence as we commonly think of it; it is, rather, a kind of subtle but persuasive aroma emanating from the inner part of the personality.
A jerk, then, is a man (or woman) who is utterly unable to see himself as he appears to others. He has no grace, he is tactless without meaning to be, he is a bore even to his best friends, he is an egotist without charm. All of us are egotists to some extent, but most of us--unlike the jerk--are perfectly and horribly aware of it when we make asses of ourselves. The jerk never knows.
The whole essay here: