NOUN (3)

1. a speaker with an unusually loud voice;

2. the mythical Greek warrior with an unusually loud voice who died after losing a shouting contest with Hermes;

3. any of several trumpet-shaped ciliate protozoans that are members of the genus Stentor;

The Collaborative International Dictionary of English v.0.48:

Stentor \Sten"tor\, n. [L. Stentor, Gr. ?.]
   1. A herald, in the Iliad, who had a very loud voice; hence,
      any person having a powerful voice.
      [1913 Webster]

   2. (Zool.) Any species of ciliated Infusoria belonging to the
      genus Stentor and allied genera, common in fresh water.
      The stentors have a bell-shaped, or cornucopia-like, body
      with a circle of cilia around the spiral terminal disk.
      See Illust. under Heterotricha.
      [1913 Webster]

   3. (Zool.) A howling monkey, or howler.
      [1913 Webster]

WordNet (r) 3.0 (2006):

stentor
    n 1: a speaker with an unusually loud voice
    2: the mythical Greek warrior with an unusually loud voice who
       died after losing a shouting contest with Hermes
    3: any of several trumpet-shaped ciliate protozoans that are
       members of the genus Stentor