To mediate, to be an intermediate.
To arrange, in the manner of a broker.
Any substance formed as part of a series of chemical reactions that is not the end-product.
An intermediary.
Anything in an intermediate position.
Being between two extremes, or in the middle of a range.
To establish a liaison.
To cooperate, consult and discuss in order to come to a common solution.
To act between parties with a view to reconciling differences.