Allegheny Alleghenian • allegiance · · · Info · Definitions · Characters · · Allegheny · · Text Latin · · Script 9 · · Length Definitions · · · (noun) a river that rises in Pennsylvania and flows north into New York and then back south through Pennsylvania again to join the Monongahela River at Pittsburgh which is the beginning of the Ohio River. Synonyms: Allegheny River. · · Noun Definition 1 Characters · · A latin capital letter a U+0041 e latin small letter e U+0065 g latin small letter g U+0067 h latin small letter h U+0068 l latin small letter l U+006C n latin small letter n U+006E y latin small letter y U+0079