in·ter·me·di·ary 
/ˌɪntɚˈmi:diˌeri/ noun
plural in·ter·me·di·ar·ies /ˌɪntɚˈmi:diˌeri/ noun [count] : a person who works with opposing sides in an argument or dispute in order to bring about an agreement
▪ He served as an intermediary between the workers and the executives.
▪ He served as an intermediary between the workers and the executives.
— intermediary adjective
▪ He was an intermediary agent in the negotiations.
▪ He was an intermediary agent in the negotiations.
