[mas.to.don] n [NL mastodont-, mastodon, fr. Gk mastos + odont-, odon, odous tooth--more at tooth] (1813) 1: any of numerous extinct mammals (genus Mastodon syn. Mammut) that differ from the related mammoths and existing elephants chiefly in the form of the molar teeth
2: one that is unusually large -- mas.to.don.ic adj -- mas.to.dont adj or n