nut·gall (n?t?gôl?)n. A nutlike gall. Nutgalls on certain oak trees were formerly used as a source of tannic acid for making ink and dye. Also called gallnut.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.nutgall (?n?t????l) n (Plant Pathology) a nut-shaped gall caused by gall wasps on the oak and other treesCollins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014nut?gall (?n?t?g?l) n. a small nutlike gall, esp. one on an oak. Random House Kernerman Webster’s College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.