D defs.my
Entry 1 sense Webster, 1913

Ironsides

/ī'-ẽrn-sīdzˌ/ · I·ron·sides · IPA /ˈaɪərnsˌaɪdz/
01 n. A cuirassier or cuirassiers; also, hardy veteran soldiers; -- applied specifically to Cromwell's cavalry.
  1. 1.
    A cuirassier or cuirassiers; also, hardy veteran soldiers; -- applied specifically to Cromwell's cavalry.
Phrases & compounds
Old Ironsides — 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.