Openly, directly, as in I do not have the nerve to tell him to his face that he wasn't invited and shouldn't have come. This idiom alludes to a direct confrontation. [Mid-1500s]
The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.