Source : Webster's Revised Unabridged Dictionary (1913)

Sky-high \Sky"-high`\, adv. & a.
   Very high. [Colloq.]

Source : WordNet®

sky-high
     adv 1: (with verb `to blow') destroyed completely; blown apart or
            to pieces; "they blew the bridge sky-high"; "the
            committee blew the thesis sky-high"
     2: in a lavish or enthusiastic manner; "he extolled her virtues
        sky-high" [syn: {enthusiastically}]
     3: to a very high level; "prices have gone sky-high"; "garbage
        was piled sky-high"; "the men were flung sky-high by the
        explosion"