Source : Webster's Revised Unabridged Dictionary (1913)

Spadefoot \Spade"foot`\, n. (Zo["o]l.)
   Any species of burrowing toads of the genus {Scaphiopus},
   esp. {S. Holbrookii}, of the Eastern United States; -- called
   also {spade toad}.

Source : WordNet®

spadefoot
     n : burrowing toad of the northern hemisphere with a horny
         spade-like projection on each hind foot [syn: {spadefoot
         toad}]