Source : Webster's Revised Unabridged Dictionary (1913)

Massy \Mass"y\, a. [Compar. {Massier}; superl. {Massiest}.]
   Compacted into, or consisting of, a mass; having bulk and
   weight ot substance; ponderous; bulky and heavy; weight;
   heavy; as, a massy shield; a massy rock.

         Your swords are now too massy for your strengths, And
         will not be uplifted.                    --Shak.

         Yawning rocks in massy fragments fly.    --Pope.

Source : WordNet®

massiest
     See {massy}