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8.
a word derived from the words "RAD"(commonly all capitalized) and "fantastic", in a way of saying better then RAD or Fantastic but in the sense of being rad or fantastic
RADtastic mainly used in small towns or areas made up in the city of Bellevue Nebraska while describing SKA music
a commonly used phrase with RADtastic is
"RADtastically SKAwesome"
"Dude, thats RADtastic!"
"RADtastically SKAwesome
by RADtastically SKAwesome January 11, 2007
 
9.
fully radical;rad and fantastic at the point of full expression at the same time.
That show last night was fucking radtastic, dude!!
by Andy-Fuckin-V!!!! February 25, 2012
 
10.
Totally cool, yet better then life.

Related to the words rad and awesome.
"That shirt is radtastic man."
by AudreyDoodleBop July 31, 2009
 
11.
Extremely rad.
Really "cool".
Amazing.
Sarah is radtasic.
Ashley, that stunt was so "rad". Radtastic
Tonight is going to be so radtsatic.
Tonight is going to be so rad.
by Holly. October 07, 2007