former partner

noun
  1. A person with whom one was previously in a romantic or business relationship. noun
    She ran into her former partner at the conference and they had a brief conversation.
    After the breakup, he found it difficult to remain friends with his former partner.
  2. A person who was once a member of a partnership, such as in a business or professional context, but is no longer involved. noun
    The former partner of the law firm decided to start his own practice.
    After the merger, she became a former partner of the company and moved on to new ventures.