mediator-n; 2 Senses

Sense Number 1: an arbitrator or intermediary in a conflict

Commentary: MEDIATOR[+person][+intermediary][+conflict] [+role][+arbitrator]

France has also sent a mediator to the negotiations.
The couple decided to use a mediator to settle their divorce out of court.

WordNet 3.0 Sense Numbers: 1

Sense Number 2: an instigating agent in a physical process

Commentary: MEDIATOR[+substance][+chemical] [+role][+agent][+instigator][+response]

Histamine and heparin are allergy mediators released by mast cells in contact with an allergen.
There is some unknown biochemical mediator involved in this cell response.

WordNet 0.0 Sense Numbers: 2