dialog boxn. A window that appears on a computer screen, presenting information or requesting input.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.di?alog box` n. Computers. (in a graphical user interface) a box, called up temporarily on the screen, that asks for user input. Random House Kernerman Webster’s College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.