The Collaborative International Dictionary of English v.0.48:

Grenadier \Gren`a*dier"\, n. [F. grenadier. See Grenade.]
   1. (Mil.) Originaly, a soldier who carried and threw
      grenades; afterward, one of a company attached to each
      regiment or battalion, taking post on the right of the
      line, and wearing a peculiar uniform. In modern times, a
      member of a special regiment or corps; as, a grenadier of
      the guard of Napoleon I. one of the regiment of Grenadier
      Guards of the British army, etc.
      [1913 Webster]

   Note: The feats of grenadiers have been memorialized in song,
         as in the following: (for the melody see
         http://www.acronet.net/~robokopp/english.html)
         Some talk of Alexander, and some of Hercules / The
         British Grenadiers ca. 18th Century The British
         Grenadiers
         Some talk of Alexander,
         And some of Hercules
         Of Hector and Lysander,
         And such great names as these.
         But of all the world's great heroes,
         There's none that can compare
         With a tow, row, row, row, row, row,
         To the British Grenadier.
         2. Those heroes of antiquity
         Ne'er saw a cannon ball
         Or knew the force of powder
         To slay their foes withall.
         But our brave boys do know it,
         And banish all their fears,
         Sing tow, row, row, row, row, row,
         For the British Grenadier.
         3. Whene'er we are commanded
         To storm the palisades
         Our leaders march with fusees,
         And we with hand grenades.
         We throw them from the glacis,
         About the enemies' ears.
         Sing tow, row, row, row, row, row,
         The British Grenadiers.
         4. And when the siege is over,
         We to the town repair
         The townsmen cry, "Hurra, boys,
         Here comes a Grenadier!"
         Here come the Grenadiers, my boys,
         Who know no doubts or fears!
         Then sing tow, row, row, row, row, row,
         The British Grenadiers.
         5. Then let us fill a bumper,
         And drink a health to those
         Who carry caps and pouches,
         And wear the louped clothes.
         May they and their commanders
         Live happy all their years
         With a tow, row, row, row, row, row,
         For the British Grenadiers.

   2. (Zool.) Any marine fish of the genus Macrurus, in which
      the body and tail taper to a point; they mostly inhabit
      the deep sea; -- called also onion fish, and rat-tail
      fish.
      [1913 Webster]

   3. (Zool.) A bright-colored South African grosbeak
      (Pyromelana orix), having the back red and the lower
      parts black.
      [1913 Webster]