Hornbeam \Horn"beam`\, n. [See {Beam}.] (Bot.) A tree of the genus {Carpinus} ({Carpinus Americana}), having a smooth gray bark and a ridged trunk, the wood being white and very hard. It is common along the banks of streams in the United States, and is also called {ironwood}. The English hornbeam is {Carpinus Betulus}. The American is called also {blue beech} and {water beech}. [1913 Webster] {Hop hornbeam}. (Bot.) See under {Hop}. [1913 Webster]