Source : Webster's Revised Unabridged Dictionary (1913)

Bucktooth \Buck"tooth`\, n.
   Any tooth that juts out.

         When he laughed, two white buckteeth protruded.
                                                  --Thackeray.

Source : WordNet®

bucktooth
     n : a large projecting front tooth
     [also: {buckteeth} (pl)]