Source : Webster's Revised Unabridged Dictionary (1913)

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.

   2. Hence, an extreme or radical republican; a violent
      revolutionist; a Jacobin.