The Collaborative International Dictionary of English v.0.48:

Sanhedrin \San"he*drin\, Sanhedrim \San"he*drim\, n. [Heb.
   sanhedr[imac]n, fr. Gr. ?; ? with + ? a seat, fr. ? to sit.
   See Sit.] (Jewish Antiq.)
   the great council of the Jews, which consisted of seventy
   members, to whom the high priest was added. It had
   jurisdiction of religious matters.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Synagogue \Syn"a*gogue\, n. [F., from L. synagoga, Gr. ? a
   bringing together, an assembly, a synagogue, fr. ? to bring
   together; sy`n with + ? to lead. See Syn-, and Agent.]
   1. A congregation or assembly of Jews met for the purpose of
      worship, or the performance of religious rites.
      [1913 Webster]

   2. The building or place appropriated to the religious
      worship of the Jews.
      [1913 Webster]

   3. The council of, probably, 120 members among the Jews,
      first appointed after the return from the Babylonish
      captivity; -- called also the Great Synagogue, and
      sometimes, though erroneously, the Sanhedrin.
      [1913 Webster]

   4. A congregation in the early Christian church.
      [1913 Webster]

            My brethren, . . . if there come into your synagogue
            a man with a gold ring.               --James ii.
                                                  1,2 (Rev.
                                                  Ver.).
      [1913 Webster]

   5. Any assembly of men. [Obs. or R.] --Milton.
      [1913 Webster]

WordNet (r) 3.0 (2006):

Sanhedrin
    n 1: the supreme judicial and ecclesiastical council of ancient
         Jerusalem

Hitchcock's Bible Names Dictionary (late 1800's):

Sanhedrin, sitting together