moderator UK US /ˈmɒdəreɪtər/ noun [C]
someone who controls and leads a discussion between a group of people, but does not take any side in it: »

A panel of business people will ask the candidates questions, with a local journalist as moderator.

Compare MEDIATOR(Cf. ↑mediator)
INTERNET someone who makes sure that the rules of an internet discussion are not broken, for example by removing any threatening or offensive comments: »

She began posting on the message board and was later asked to be a moderator.

Financial and business terms. 2012.