rimrock

[rim-rok]

noun Geology.

rock forming the natural boundary of a plateau or other rise.
bedrock forming the natural boundary of a placer or of a gravel deposit.

Origin of rimrock

An Americanism dating back to 1855–60; rim + rock¹

Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

Examples from the Web for rimrock

Historical Examples of rimrock

We followed along the ledge around the rimrock until we came to a little pass through.
Pluck on the Long Trail
Edwin L. Sabin
On either side were brownish red jagged peaks and rimrock faces, specked with snow.
Pluck on the Long Trail
Edwin L. Sabin
One after another they leaped over the edge of the rimrock until most of the flock was destroyed.
The Story of Wool
Sara Ware Bassett
The rimrock and the gravels above and below it constitute the Rattlesnake Formation.
The Geologic Setting of the John Day Country
Thomas Prence Thayer

British Dictionary definitions for rimrock

rimrock

noun

rock forming the boundaries of a sandy or gravelly alluvial deposit

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