Definitions of Manchu:

noun: the Tungusic language spoken by the Manchu people
noun: a member of the Manchu speaking people of Mongolian race of Manchuria; related to the Tungus; conquered China in the 17th century
noun: 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