For the sake of appearances or display. For example, They put on a lavish buffet, mainly for show, or The police pretended to jail the informer, for show. [c. 1700]
The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.