noun Geology.

a fragmental rock consisting of the smaller kinds of volcanic detritus, as ash or cinder, usually more or less stratified.

Origin of tuff

1560–70; < French tuf < Italian tufo. See tufa
Also called volcanic tuff.
Related formstuff·a·ceous [tuh-fey-shuh s] /tʌˈfeɪ ʃəs/, adjective
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

Examples from the Web for tuffaceous

Historical Examples of tuffaceous

  • Agglomeratic and tuffaceous rocks are of quite common occurrence, although less important than the lavas.

British Dictionary definitions for tuffaceous



a rock formed by the fusing together on the ground of small rock fragments (less than 2 mm across) ejected from a volcano
Derived Formstuffaceous (tʌˈfeɪʃəs), adjective

Word Origin for tuff

C16: from Old French tuf, from Italian tufo; see tufa
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 tuffaceous



advertiser's spelling of tough (adj.), attested by 1940.

Online Etymology Dictionary, © 2010 Douglas Harper

tuffaceous in Science



A rock made up of particles of volcanic ash, varying in size from fine sand to coarse gravel.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.