Not decolorized by acid after staining, as bacteria that retain dye after an acid rinse.(adjective)
American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Use "acid-fast" in a sentence
"It belongs to that small group known as acid-fast bacteria."
"(This often, but not invariably, removes the stain from acid-fast bacilli other than tubercle; e. g., smegma bacillus.) 7."
"~ -- (To demonstrate tubercle and other acid-fast bacilli.) 1."