Source : Webster's Revised Unabridged Dictionary (1913)

Upthrow \Up*throw"\, v. t.
   To throw up. --Drayton.

Upthrow \Up"throw`\, n. (Mining)
   See {Throw}, n., 9.

Source : WordNet®

upthrow
     n : (geology) a rise of land to a higher elevation (as in the
         process of mountain building) [syn: {upheaval}, {uplift},
          {upthrust}]