trĭăs, ădis, f., = τριάς,
the number three , a triad , Mart. Cap. 7, § 733.
·noun The formation situated between the Permian and Lias, and so named by the Germans, because cons...
Webster's Dictionary of the English Language
·noun A term applied to many American Mesozoic strata, in which the characteristics of the Jurassic ...