Source : Webster's Revised Unabridged Dictionary (1913)

Columbiad \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}.