Definition of Maggie's drawers in English:

Maggie's drawers

noun

military slangUS
  • 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.