[ pahy-ruh-klas-tik ]
/ ˌpaɪ rəˈklæs tɪk /

adjective Geology.

composed chiefly of fragments of volcanic origin, as agglomerate, tuff, and certain other rocks; volcaniclastic.

Origin of pyroclastic

First recorded in 1885–90; pyro- + clastic Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

British Dictionary definitions for pyroclastic


/ (ˌpaɪrəʊˈklæstɪk) /


(of rocks) formed from the solid fragments ejected during a volcanic eruption
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

Word Origin and History for pyroclastic



1887, from pyro- + clastic.

Online Etymology Dictionary, © 2010 Douglas Harper

Science definitions for pyroclastic


[ pī′rō-klăstĭk ]

Composed chiefly of rock fragments of explosive origin, especially those associated with explosive volcanic eruptions. Volcanic ash, obsidian, and pumice are examples of pyroclastic materials.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.