(n.) One who negotiates; a person who treats with others, either as principal or agent, in respect to purchase and sale, or public compacts.

agent arbitrator bargainer broker business agent cardholder connection contact deputy front front man go-between interagent interceder intercessor intermediary intermediate intermediate agent intermediator intermedium internuncio interpleader intervener interventionist interventor labor organizer mediator medium middleman mouthpiece negotiant negotiatress negotiatrix ombudsman organizer shop steward spokesman spokeswoman trade unionist union member union officer unionist