The Collaborative International Dictionary of English v.0.48:

ronin \ro"nin"\ (r[=o]"n[i^]n), n. [Jap. r[=o]-nin, fr. Chin.
   lang profligate, lawless + j[^e]n (old sound n[imac]n) man.]
   In Japan, under the feudal system, a samurai who had
   renounced his clan or who had been discharged or ostracized
   and had become a wanderer without a lord; an outcast; an
   outlaw.
   [Webster 1913 Suppl.] Ronion