Originates from the DC Comic cartoon
character - The Flash.
It is used to describe things that are superhumanly amazing, and awesome, pretty much THE best thing EVER.
It can also be used as an alternate form of the word "go" when playing games.
Typically it is best used to describe activities that you want
kids to get REALLY
stoked about.
Alright guys! This
game of dodgeball is going to be FLASHTASTIC!
Ok
kids, when I say "flashtastic" you are all going to spin around 20 times and then begin!!!
Those
tater-tots are flashtastic. totally.