Definition 1: A complimentary statement of one's posterior.
Definition 2: A durogatory comment regarding someone who excels at being a fantastic asshole.
Synonym: Colossus Assholus
Example 2: "My ex was asstastic, he left me destitute."
2. When used in a situation, this means you are not satisfied with the outcome.
2. I'm going to the dentist today, this shit's asstastic.