Without any possible doubt. You know full well why I'm upset with you, so there's no use playing dumb! We know full well that many families are struggling to make ends meet, but these tax increases are unavoidable.
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.
Very well, exceedingly well, as in You know full well how much this costs. [c. 1700]
The American Heritage® Dictionary of Idioms by Christine Ammer. Copyright © 2003, 1997 by The Christine Ammer 1992 Trust. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.