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 be inserted between parts or things; to come between.
To interrupt a conversation by introducing a different subject or making a comment.
To intervene in a dispute, or in a conversation.
To insert something (or oneself) between other things.
To offer (one's help or services).