The Collaborative International Dictionary
Massiest
Massy \Mass"y\, a. [Compar. Massier; superl. Massiest.] Compacted into, or consisting of, a mass; having bulk and weight or substance; ponderous; bulky and heavy; weighty; 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.
Wiktionary
massiest
a. (en-superlative of: massy)
WordNet
massiest
See massy