arbitrator; mediator; person who settles a dispute
Refers to a person who steps in to resolve a conflict or argument, often in a group setting. Can be used in both formal and informal contexts.
When opinions clashed at the meeting, he stepped in as the arbitrator.
The older sister always acts as the mediator in the children's fights.
Compound of 留め (tome, 'stopping') + 役 (yaku, 'role'). Literally 'the role of stopping', referring to a person whose function is to halt or settle disputes.