An individual source or item of (private or public) income; (also) the amount of income deriving from this.

A possible source of revenue.

An object of extortion; a source of profit or pecuniary advantage.

North American. figurative. The source of the rewards of political office, esp. political patronage.

In various figurative phrases applied to a ready source of income, esp. one shared by unscrupulous persons. colloquial.

(a sector of) a business which provides a steady cash flow, esp. one considered as an attractive take-over target.