'Copartner' definitions:

Definition of 'copartner'

From: WordNet
noun
A joint partner (as in a business enterprise)

Definition of 'Copartner'

From: GCIDE
  • Copartner \Co*part"ner\, n. One who is jointly concerned with one or more persons in business, etc.; a partner; an associate; a partaker; a sharer. [1913 Webster]
  • the associates and copartners of our loss. --Milton. [1913 Webster]