[ trahy-as-ik ]
/ traɪˈæs ɪk /


noting or pertaining to a period of the Mesozoic Era, occurring from 230 to 190 million years ago and characterized by the advent of dinosaurs and coniferous forests.


Also Tri·as [trahy-uh s] /ˈtraɪ əs/ the Triassic Period or System.

Origin of Triassic

1835–45; Trias the three-part series of strata characterizing the period (< German < Greek triás; see triad) + -ic

Related forms

post-Tri·as·sic, adjective Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

Examples from the Web for triassic

British Dictionary definitions for triassic


/ (traɪˈæsɪk) /


of, denoting, or formed in the first period of the Mesozoic era that lasted for 42 million years and during which reptiles flourished


the Triassic or Trias the Triassic period or rock system

Word Origin for Triassic

C19: from Latin trias triad, with reference to the three subdivisions
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Science definitions for triassic


[ trī-ăsĭk ]

The earliest period of the Mesozoic Era, from about 245 to 208 million years ago. During the early part of the Triassic Period the supercontinent Pangaea was located along the equator; by the end of the Triassic it had started to split up. Land life diversified in the Triassic in response to the mass extinctions of the end of the Paleozoic. Conifers, cycads, marine reptiles, dinosaurs, and the earliest mammals first appeared. See Chart at geologic time.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.