Sans-culotte

‖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 ]