1. A snide description of an action or event that lacks legitimacy.
(Legitimacy as pertaining to the feelings of the person issuing the comment)
2. Sharp disapproval of ones actions, affiliations, opinions, beliefs or rhetoric.
That class was jackassticly long.
The free masons are a jackastic organization.
Denial that CO2 emissions are responsible for global warming is jackasstic.
Harris county is jackassticly overpopulated.
Using sarcasm in an overtly apparent manner. Usually to your friends. Displaying extreme ignorance and using sarcasm to cover it up.
Ex: You are so jackasstic when you talk about Star Trek.
Ex: My old roomate constantly makes jackasstic comments about things he does not know.