noun Geology.

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

Nearby words

  1. tuesday,
  2. tuesdays,
  3. tuf,
  4. tufa,
  5. tufaceous,
  6. tuffaceous,
  7. tuffet,
  8. tuffstone body,
  9. tuft,
  10. tufted

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

  • 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

Science definitions for tuffaceous



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.