brush off

verb
  1. 1

    To disregard (something), to dismiss or ignore (someone), as unimportant.

  2. 2

    To depart with a sweeping motion.

noun
  1. 1

    An abrupt rebuff, a snub or curt rejection, a disdainful dismissal.

    โ€œA halfhearted โ€œthank youโ€ may be a brush-off.โ€

Source: https://en.wiktionary.org/wiki/brush%20off, https://en.wiktionary.org/wiki/brush-off