The Collaborative International Dictionary of English v.0.48:

Manumit \Man`u*mit"\, v. t. [imp. & p. p. Manumitted; p. pr. &
   vb. n. Manumitting.] [L. manumittere, manumissum; manus the
   hand + mittere to send, to send off. See Manual, and
   Missile.]
   To release from slavery; to liberate from personal bondage or
   servitude; to free, as a slave. "Manumitted slaves." --Hume.
   [1913 Webster]

WordNet (r) 3.0 (2006):

manumit
    v 1: free from slavery or servitude [syn: manumit,
         emancipate]