Definition of Maggie's drawers in English:

Maggie's drawers

noun

US
military slang
  • A red flag used to indicate a miss in target practice.

    • ‘If the slang term "Maggie's drawers" was in use during World War I, the reference was probably too indelicate for many printed examples to exist.’
    • ‘Evidently "Maggie's drawers" was inspired by the title of a bawdy song on that very subject.’

Origin

1940s: said to be in reference to a song entitled Those Old Red Flannel Drawers That Maggie Wore.