/ Dictionary / Index A Anacostia River: Meaning and Definition of Find definitions for: Anacos'tia Riv'er Pronunciation: [key] a river in the District of Columbia flowing into the Potomac River. ab. 24 mi. (39 km) long. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. Anacostia anacoustic Related Content Daily Word Quiz: immense Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language