Co*lum"bi*ad (?), n. [From Columbia the United States.] (Mil.) A form of seacoast cannon; a long, chambered gun designed for throwing shot or shells with heavy charges of powder, at high angles of elevation.

&fist; Since the War of 1812 the Columbiad has been much modified, especially by General Rodman, and the improved form now used in seacoast defense is often called the Rodman gun.