A member of a civil partnership

A criminal accomplice. / (informal, humorous) A close associate.

(business) A partner who is not actively involved in the running of a business. / Used other than figuratively or idiomatically: see silent, partner.

(UK) A business partner who doesn't play an active role in running the day-to-day operations of a business, who instead, finances the business in the form of capital investment.

(business) A fellow business professional who acts as a moderating influence and mentor

Involving multiple partners.

(soccer) A fellow striker.

A partner in a business context (as opposed to a partner in the sense of a personal relationship).

Either an associate government or non-government entity or agency that supplements the works of a larger organization or agency by helping to carry out institutional arrangements in line with the larger organization's goals and objectives.

Someone that one has sex with, especially on an informal or casual basis.