- a fragmental rock consisting of the smaller kinds of volcanic detritus, as ash or cinder, usually more or less stratified.
Origin of tuff2
1560–70; < French tuf < Italian tufo. See tufa
Also called volcanic tuff.
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018
Examples from the Web for tuffaceous
Agglomeratic and tuffaceous rocks are of quite common occurrence, although less important than the lavas.Mount Rainier
- a rock formed by the fusing together on the ground of small rock fragments (less than 2 mm across) ejected from a volcano
C16: from Old French tuf, from Italian tufo; see tufa
Word Origin and History for tuffaceous
advertiser's spelling of tough (adj.), attested by 1940.
Online Etymology Dictionary, © 2010 Douglas Harper
- 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.