3. without a bindingsaid as of a book
4. not held in physical or chemical union with another element, substance, etc.; free
⇒ unbound electrons
Webster’s New World College Dictionary, Fourth Edition, compiled by the
editors of Webster’s New World Dictionaries. Copyright © 2010 by Houghton
Mifflin Harcourt. Published by Houghton Mifflin Harcourt. All rights reserved.