in·ter·bank (?n?t?r-b?ngk?)adj. Of or relating to transactions or communication between banks: interbank borrowing.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.interbank (?nt??bæ?k) adj (Banking & Finance) conducted between or involving two or more banksCollins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014