Sans-culotte

from The Collaborative International Dictionary of English v.0.48

Sans-culotte \Sans`-cu`lotte"\ (F. ?; E. ?), n. [F., without
   breeches.]
   1. A fellow without breeches; a ragged fellow; -- a name of
      reproach given in the first French revolution to the
      extreme republican party, who rejected breeches as an
      emblem peculiar to the upper classes or aristocracy, and
      adopted pantaloons.
      [1913 Webster]

   2. Hence, an extreme or radical republican; a violent
      revolutionist; a Jacobin.
      [1913 Webster]