An intermediary.
Any substance formed as part of a series of chemical reactions that is not the end-product.
Anything in an intermediate position.
To mediate, to be an intermediate.
To arrange, in the manner of a broker.
Being between two extremes, or in the middle of a range.
A person of minor significance, accomplishment or acclaim; a common and undistinguished person.
A member of a socioeconomic class between the upper ranks of society and the agricultural workers.
Having no peculiar or outstanding features; not extraordinary, special, exceptional, or great; of medium quality, almost always with a negative connotation.