/ Dictionary / Index A Allegheny: Meaning and Definition of Find definitions for: Al•le•ghe•ny Pronunciation: (al"i-gā'nē), [key] — n. a river flowing NW from Pennsylvania into SW New York and then S through W Pennsylvania, joining the Monongahela at Pittsburgh to form the Ohio River. 325 mi. (525 km) long. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: allegheny (Thesaurus) allegedly Allegheny barberry Related Content Daily Word Quiz: perspicacious Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language