Definition of fat-mouth in English:

fat-mouth

noun

US
slang
  • One who talks extravagantly, a loudmouth.

verb

US
slang, black english
  • 1no object To talk a great deal about something, with little or no action or result.

  • 2with object To talk excessively to, especially in order to cajole or sweet-talk.

Origin

1940s; earliest use found in Lester V. Berrey (b. 1907), lexicographer<br>1970s; earliest use found in The Atlantic Monthly.