ironsides

n. A cuirassier or cuirassiers; also, hardy veteran soldiers; -- applied specifically to Cromwell's cavalry.

Old Ironsides. (U. S. Hist.) A nickname for the U.S.S. Constitution, a sailing ship which fought in the American Revolutionary war, and now functions as a floating museum in Boston harbor. It was given its nickname because cannonballs bounced off its hard wooden sides. [ PJC ]