What does you're a jerk mean?

A jerk can be defined as "an inconsiderate person" or, "somebody who is regarded as behaving foolishly." It is considered an offensive term.

"Jerk" is most commonly used to label a disrespectful, somewhat cruel, or otherwise "mean" individual.

"Jerk" can also be applied as, "don't be a jerk," or "Jason is being a huge jerk." In this case, it refers to the subject's negative behavior towards another party in that instance, and not necessarily to the subject's general behavior the majority of the time.