1
general::
Dismiss or rebuff, as in Roberta brushed off the poor reviews with a shrug, or You can't brush off a boyfriend and expect him to do you a favor. This expression, transferring sweeping off crumbs to a curt dismissal, was first recorded about 1820. However, it became common usage only in the 1930s. Also see GIVE SOMEONE THE AIR (BRUSHOFF).
American Heritage Idioms
2
general::
Phrase(s): brush something off someone or something [and] brush something off
to remove something from someone or something by brushing. • I brushed a little lint off her collar. • I brushed off the lint that was on her collar., Phrase(s): brush someone off
1. Lit. to remove something, such as dust or lint, from someone by brushing. • The bathroom attendant brushed Mr. Harris off and was rewarded with a small tip. • The porter had never brushed off such a miserly man before. 2. Fig. to reject someone; to dismiss someone. (As if someone were mere lint.) • He brushed her off, telling her she had no appointment. • He brushed off Mrs. Franklin, who was only trying to be nice to him., Phrase(s): *the brush-off
Fig. rejection; being cast aside and ignored. (*Typically: get ~; give someone ~.) • Don’t talk to Tom. He’ll just give you the brush-off. • I went up to her and asked for a date, but I got the brush-off.
McGrawhill's American Idioms And Phrasal Verbs