To cause something to become puffier in appearance. A noun or pronoun can be used between "fluff" and "out." In the 80s, girls used to fluff out their bangs and make their hair as voluminous as possible.
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.
fluff something out
[for a bird] to move its feathers outward. The parrot said good night, fluffed its feathers out, and went to sleep. The bird fluffed out its feathers.
McGraw-Hill Dictionary of American Idioms and Phrasal Verbs. © 2002 by The McGraw-Hill Companies, Inc.