noun

• (with "the") The Allegheny River in Pennsylvania.
• Allegheny Mountain (Pennsylvania), a major mountain ridge in the northern part of the Allegheny Mountains.
• Allegheny Mountain (West Virginia – Virginia), a major mountain ridge in the southern part of the Allegheny Mountains.
• (dated, attributively) The Allegheny Mountains.
• (dated, attributively) Appalachia.
• Any of several towns or counties in Pennsylvania, Virginia, North Carolina and Kentucky.