C horizonn. In ABC soil, the lowermost zone, consisting mainly of unconsolidated, weathered rock fragments.American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.C horizon n (Geological Science) the layer of a soil profile immediately below the B horizon and above the bedrock, composed of weathered rock little affected by soil-forming processes Collins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014C horizon n. the layer in a soil profile below the B horizon and immediately above the bedrock, consisting chiefly of weathered, partially decomposed rock. [1930?35] Random House Kernerman Webster’s College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.