tact·ful (t?kt?f?l)adj. Possessing or exhibiting tact; considerate and discreet: a tactful person; a tactful remark.tact?ful·ly adv.tact?ful·ness n.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.tact?ful (?tækt f?l) adj. having or manifesting tact. [1860?65] tact?ful?ly, adv. tact?ful?ness, n. syn: See diplomatic. Random House Kernerman Webster’s College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.