Source : Webster's Revised Unabridged Dictionary (1913)

Solidarity \Sol`i*dar"i*ty\, n. [F. solidarit['e], fr. solide.
   See {Solid}.]
   An entire union or consolidation of interests and
   responsibilities; fellowship; community.

         Solidarity [a word which we owe to the French
         Communists], signifies a fellowship in gain and loss,
         in honor and dishonor, in victory and defeat, a being,
         so to speak, all in the same boat.       --Trench.

         The solidarity . . . of Breton and Welsh poetry. --M.
                                                  Arnold.

Source : WordNet®

solidarity
     n : a union of interests or purposes or sympathies among members
         of a group