B horizonn. In ABC soil, the second and middle zone, characterized by an accumulation of soluble or suspended organic material, clay, iron, or aluminum. Also called zone of accumulation, zone of illuviation.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.B horizon n (Physical Geography) the layer of a soil profile immediately below the A horizon, containing deposits of leached material Collins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014B horizon n. the subsoil in a soil profile. [1935?40] Random House Kernerman Webster’s College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.