Adj: When a cup/glass/mug/goblet is just so awesome that you need to describe it.
Noun: A great experience that makes you think of a cool glass or drink that you've had.
Ex.1
A: Like my new mug?
B: Oh yeah! Its mug-tastic!
Ex.2
*Person A just totally nails an awesome skate trick and thinks about how the great glass of chocolate milk they had today helped them do it.*
A: "MUG-TASTIC!!!"