Adjective.
Definition 1: A complimentary statement of one's posterior.
Synonym: Bootylicious

Definition 2: A durogatory comment regarding someone who excels at being a fantastic asshole.
Synonym: Colossus Assholus

the whale tail is the shape formed when a g-string rides up high over a womans trousers

(adj.)having a great ass

1. Extremely bad; abominable
2. Extremely evil or cruel

1. When talking about a person, it's a good term, meaning they are attractive in the ass department.

2. When used in a situation, this means you are not satisfied with the outcome.

An adjective that one exclaims when they see a sexy looking behind.

Asstastic is a combination of "Ass" and "Fantastic." Was created as a satire of all words that ironically mean "excellent," such as cool, wicked, tight, gnarly and sick.