This is a term mostly used by those involved with Wheel of Fortune. It means fantastic, but the "fan" is changed to "spin", referencing the wheel in the popular game show. Pat Sajak, the host, has said this phrase a few times, which is how it stuck with the audience.
The epitome of awesome. Usually used to describe an event that is remarkably positive in ones favor. Also can be used to describe the immediate boner you get when a chick is super uberhot.
If one makes all of their opponents cups on a rebuddle in beer pong its shwingtastic.
Guy: Dude I heard you fucking in your room last night 8 doors down the hallways!
Guy 2: I know! It was shwingtastic.
Nickname given to bales of marijuana thrown overboard or out of airplanes. Origin is reportedly from members of the US Coast Guard in the area of Southern Florida.