eth·am·bu·tol (?-th?m?by?-tôl?, -t?l?, -t?l?)n. An antibacterial drug, C10H24N2O2, used in a hydrochloride form with other drugs to treat pulmonary tuberculosis.[eth(ylene) + am(ine) + but(an)ol.]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.ethambutol (???æmbj??t?l) n (Pharmacology) a compound used in the treatment of tuberculosis[from eth(ylene) + am(ine) + but(an)ol]Collins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014