Tb 1The symbol for terbium.Tb 2abbr. Bible TobitTBabbr.1. tailback2. terabyte3. trial balance4. also t.b.a. tubercle bacillusb. tuberculosisAmerican 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.