The Collaborative International Dictionary of English v.0.48:

Sudra \Su"dra\ (s[=oo]"dr[.a]), n. [Skr. [,c][=u]dra.]
   The lowest of the four great castes among the Hindoos. See
   Caste. [Written also Soorah, Soodra, and Sooder.]
   [1913 Webster]