Here's John Stewart
Mill's Defense of Utilitarianism; about as succinct a paragraph as you could expect from a Nineteenth Century Philosopher:
"Utility is often summarily stigmatised as an immoral
doctrine by giving it the name of Expediency, and taking advantage of the
popular use of that term to contrast it with Principle. But the Expedient, in
the sense in which it is opposed to the Right, generally means that which is
expedient for the particular interest of the agent himself; as when a minister
sacrifices the interests of his country to keep himself in place. When it means
anything better than this, it means that which is expedient for some immediate
object, some temporary
purpose, but which violates a rule whose observance is expedient in a much
higher degree."
He gives us several possible definitions of expedient:
Expedient1 "that which is expedient for the particular interest of the agent himself, as when a minister sacrifices the interests of his country to keep himself in place."
Expedient2 "that which is expedient for some immediate object, some temporary purpose."
Expedient3 "a rule whose observance is expedient to a much higher degree."
Of course, as I suspect Mill knew, the differences between these expediences is a matter of interpretation. And, there are always three interpretations or more, that of the agent, that of the observer, and the "rule" which itself may be subject to interpretation.