The Collaborative International Dictionary of English v.0.48:
Gap-toothed \Gap"-toothed`\ (g[a^]p"t[=oo]tht`), a. Having conspicuous interstices between the teeth; as, his gap-toothed grin. --Dryden. [1913 Webster + WordNet 1.5]WordNet (r) 3.0 (2006):
gap-toothed adj 1: having widely spaced teeth; "his gap-toothed grin"