Definition of Triassic in US English:



  • 1Relating to or denoting the earliest period of the Mesozoic era, between the Permian and Jurassic periods.

    The Triassic lasted from about 245 million to 208 million years ago. Many new organisms appeared following the mass extinctions of the end of the Paleozoic era, including the earliest dinosaurs and ammonites and the first primitive mammals

    • ‘Triassic footprints were primarily made by early crocodilians and small dinosaurs.’
    • ‘Triassic asteroids are among the rarest of fossils, hitherto comprised of only three genera, all from Europe.’
    • ‘Low-angle unconformities can be observed between the Triassic and Jurassic rocks at outcrop scale.’
    • ‘Uppermost Permian and Triassic terrestrial sediments conformably overlie the terminal volcanic rocks.’
    • ‘Implicit in this emplacement model is that the Permian and Triassic plutonic complexes are tabular granites with length and width dimensions that are much greater than their thickness.’
    • ‘Permian and Triassic plutonic complexes comprise monzonite, granite, granodiorite or tonalite with minor gabbro and diorite.’
    • ‘In the Mesozoic section, a Triassic basin, up to 1800 m thick and roughly circular in map view, is centred SW of the present uplifted Bishri block.’
    1. 1.1as noun the Triassic" or "the Trias The Triassic period or the system of rocks deposited during it.
      • ‘Such sites are found in numerous strata of different ages throughout the triassic, jurassic and cretaceous, all of which were allegedly laid down during the flood.’


Mid 19th century: from late Latin trias (see triad), because the strata are divisible into three groups, + -ic.