The Collaborative International Dictionary of English v.0.48:

Semimute \Sem`i*mute"\, a.
   Having the faculty of speech but imperfectly developed or
   partially lost.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Semimute \Sem"i*mute`\, n.
   A semimute person.
   [1913 Webster]