To hide, cover, or conceal something, either partially or in full. He thinks he can just mask out the smell in the bathroom with that horrible deodorant spray, but it just makes everything worse. We've planted trees around the perimeter of our property to mask it out from the neighbors.
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.
mask something out
to conceal or cover part of something from view. The trees masked the city dump out, so it could not be seen from the street. The trees masked out the dump.
McGraw-Hill Dictionary of American Idioms and Phrasal Verbs. © 2002 by The McGraw-Hill Companies, Inc.