\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.
Note: 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}.