Answer: rad

AnswerCrossword Clue
RADX-ray unit
RAD"Kewl!"
RADSkatepark "great"
RADWay cool!
RADFantastic!
RADExcellent, slangily
RADOutstanding!
RADSurfspeak adjective
RADAlternative to degrees, in math: Abbr.
RAD"Cool!"
RAD"Super, man!"
RADAwesome!
RAD"Outstanding!"
RAD"Groovy!"
RADGnarly
RADAwesome
RAD"Really cool!"
RADGroovy relative?
RAD"Totally awesome!"
RAD"Gnarly!"
radto fear (to be afraid of) / radically trendy
RADHalf a diam.
RADEnergy unit
RADExtremist
RAD"Awesome!"
RADCool
RADMarvelous, slangily
RADOne-half a diam.
RADCool, these days
RADPhysicist's unit
RADTotally awesome
RADCool, in the '90s
RADWay cool
RADUnit of nuclear absorption
RADAngle measurement (abbr.)
RAD"Way cool!"
RAD"Far out!"
RAD"Totally tubular!"
RAD"Wicked!"
RADAwesome, in kidspeak