A large natural stream of water flowing in a channel to the sea, a lake, or another such stream. The Mississippi River is one of the longest rivers in the world.
A copious flow or stream of something. There was a river of tears at the farewell party.
In poker, the final community card dealt, following the turn. He was behind until the river gave him a full house.
In typography, an unintended vertical or diagonal line of white space appearing in justified text, caused by gaps between words. The poorly set paragraph was marred by noticeable rivers running down the page.