The Collaborative International Dictionary of English v.0.48:

Senate \Sen"ate\, n. [OE. senat, F. s['e]nat, fr. L. senatus,
   fr. senex, gen. senis, old, an old man. See Senior, Sir.]
   1. An assembly or council having the highest deliberative and
      legislative functions. Specifically:
      (a) (Anc. Rom.) A body of elders appointed or elected from
          among the nobles of the nation, and having supreme
          legislative authority.
          [1913 Webster]

                The senate was thus the medium through which all
                affairs of the whole government had to pass.
                                                  --Dr. W.
                                                  Smith.
          [1913 Webster]
      (b) The upper and less numerous branch of a legislature in
          various countries, as in France, in the United States,
          in most of the separate States of the United States,
          and in some Swiss cantons.
      (c) In general, a legislative body; a state council; the
          legislative department of government.
          [1913 Webster]

   2. The governing body of the Universities of Cambridge and
      London. [Eng.]
      [1913 Webster]

   3. In some American colleges, a council of elected students,
      presided over by the president of the college, to which
      are referred cases of discipline and matters of general
      concern affecting the students. [U. S.]
      [1913 Webster]

   Senate chamber, a room where a senate meets when it
      transacts business.

   Senate house, a house where a senate meets when it
      transacts business.
      [1913 Webster]