Source : Webster's Revised Unabridged Dictionary (1913)

Copartnership \Co*part"ner*ship\, n.
   1. The state of being a copartner or of having a joint
      interest in any matter.

   2. A partnership or firm; as, A. and B. have this day formed
      a copartnership.

Source : WordNet®

copartnership
     n : a partnership in which employees get a share of the profits
         in addition to their wages