Source : Webster's Revised Unabridged Dictionary (1913)

Gabbro \Gab"bro\, n. [It.] (Geol.)
   A name originally given by the Italians to a kind of
   serpentine, later to the rock called euphotide, and now
   generally used for a coarsely crystalline, igneous rock
   consisting of lamellar pyroxene (diallage) and labradorite,
   with sometimes chrysolite (olivine gabbro).

Source : WordNet®

gabbro
     n : one of a family of granular intrusive rocks