Bt (b??t??)n. A soil bacterium (Bacillus thuringiensis) that produces proteins toxic to certain insects. It has been used as an insecticide, and genes for the toxins have been incorporated into genetically modified crop plants to control insect pests.[From New Latin B(acillus) t(huringi?nsis), species name.]BTabbr. Bachelor of TheologyAmerican 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.bt abbreviation for beat bt the internet domain name for (Computer Science) Bhutan Bt abbreviation for (Heraldry) Baronet BT abbreviation for (Telecommunications) British Telecom [C20: shortened from telecommunications]Collins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014Bt. Baronet. Random House Kernerman Webster’s College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.