The Collaborative International Dictionary of English v.0.48:

Shizoku \Shi*zo"ku\, n. sing. & pl. [Jap. shi-zoku, fr. Chin.
   ch' (chi) branch, posterity + tsu kindered, class.]
   The Japanese warrior gentry or middle class, formerly called
   samurai; also, any member of this class.
   [Webster 1913 Suppl.]