rock·bound also rock-bound (r?k?bound?)adj. Hemmed in by or bordered with rocks: a rockbound lake.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.rock-bound adj (Physical Geography) hemmed in or encircled by rocks. Also (poetic): rock-girt Collins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014rock?-bound` adj. hemmed in or covered by rocks. Random House Kernerman Webster’s College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.