The Collaborative International Dictionary of English v.0.48:

Viceroy \Vice"roy\, n. [F. vice-roi; pref. vice- in the place of
   (L. vice) + roi a king, L. rex. See Vice, prep. and Royal.]
   1. The governor of a country or province who rules in the
      name of the sovereign with regal authority, as the king's
      substitute; as, the viceroy of India.
      [1913 Webster]

   2. (Zool.) A large and handsome American butterfly
      (Basilarchia archippus syn. Limenitis archippus). Its
      wings are orange-red, with black lines along the nervures
      and a row of white spots along the outer margins. The
      larvae feed on willow, poplar, and apple trees.
      [1913 Webster]

WordNet (r) 3.0 (2006):

viceroy
    n 1: governor of a country or province who rules as the
         representative of his or her king or sovereign [syn:
         viceroy, vicereine]
    2: showy American butterfly resembling the monarch but smaller
       [syn: viceroy, Limenitis archippus]

Moby Thesaurus II by Grady Ward, 1.0:

38 Moby Thesaurus words for "viceroy":
   beg, beglerbeg, bey, burgrave, collector, dey, eparch, exarch,
   gauleiter, governor, governor-general, khedive,
   lieutenant governor, nabob, nawab, palatine, proconsul, provincial,
   satrap, stadtholder, subahdar, tetrarch, vali, vice-chairman,
   vice-chancellor, vice-consul, vice-director, vice-governor,
   vice-king, vice-legate, vice-master, vice-premier, vice-president,
   vice-queen, vice-regent, vice-warden, vicegerent, wali