to·lu·i·dine (t?-lo?o??-d?n?)n. Any of three isomeric compounds, C7H9N, used to make dyes.[tolu(ene) + -id(e) + -ine.]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.toluidine (t??lju???di?n) or toluidinn (Elements & Compounds) an amine derived from toluene existing in three isomeric forms; aminotoluene. The ortho- and meta- isomers are liquids and the para- isomer is a crystalline solid. All three are used in making dyes. Formula: C6H4CH3NH2[C19: from tolu(ene) + -ide + -ine2]Collins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014to?lu?i?dine (t??lu ??din, -d?n) n. any of three isomeric amines having the formula C7H9N, derived from toluene: used in the manufacture of dyes and drugs. [1840?50; tolu (ene) + -idine] Random House Kernerman Webster’s College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.