The Collaborative International Dictionary of English v.0.48:

Manchu \Man*chu"\, a. [Written also Manchoo, Mantchoo, etc.]
   Of or pertaining to Manchuria or its inhabitants. -- n. A
   native or inhabitant of Manchuria; also, the language spoken
   by the Manchus.
   [1913 Webster]

WordNet (r) 3.0 (2006):

Manchu
    n 1: a member of the Manchu speaking people of Mongolian race of
         Manchuria; related to the Tungus; conquered China in the
         17th century
    2: the last imperial dynasty of China (from 1644 to 1912) which
       was overthrown by revolutionaries; during the Qing dynasty
       China was ruled by the Manchu [syn: Qing, Qing dynasty,
       Ch'ing, Ch'ing dynasty, Manchu, Manchu dynasty]
    3: the Tungusic language spoken by the Manchu