I won't dispute that
massy is far from common. It will be treated as rare from now on.
But, for your interest it has a multitude of meanings according to the Shorter Oxford, though all but the last one are identified as literary or archaic:
1. Solid and weighty; heavy as consisting of compact matter; (esp. of precious metals) occurring in mass, solid, not hollow or alloyed. lme.
‣†b Compact, dense. e16–e19.
‣†c Solid, having three dimensions. m16–m17.
M. Twain Its furniture was all of massy gold.
2. Consisting of a large mass or masses of heavy material; of great size and weight; (of a building) consisting of great blocks of masonry. lme.
‣b Of architectural or artistic style: presenting great masses. e19.
Ld Macaulay The massy remains of the old Norman castle.
(‣b) Modern Painters This predilection for massy stability of form is present in Moore's earliest life-drawings.
3. Of large size; voluminous, bulky; spreading in a mass or in masses. lme.
J. Updike Brick pinnacles and massy trees.
4. Of an abstract thing: great, substantial, impressive. l16.
5. Physics. = massive adjective 5. m20.
Recent examples of the word's use in English publications seem to be mainly in regard to sculpture. The
Guardian in 2017:
Outside the museum, in recent days, a new exhibit has been erected. Huge, massy, made of wood, from some angles it looks like a ruined Viking longboat lying on its side; from others, like the stretched-open, tooth-jagged jaws of a longship’s dragon figurehead.
But, to my surprise, the most frequent use of
massy is in Indian publications. Here the meaning is obviously something different, being used about movies. I couldn't find it defined anywhere, but it seems as if it might mean something or someone aiming at a mass audience. Usage examples:
Together, the three are expected to create some firebrand cinema for the massy audience on-screen.
These films also shifted the understanding of what counts as massy and commercial.
The locations for songs are colourful, classy and massy. The mass appeal makes it worth your 2 hours 45 minutes.
There were some forumites a while back arguing that, given the enormous number of English speakers in India, all English words well know to Indians (specifically, cricket terms) should be classed as common. If I'm inundated with complaints from Bollywood fans, I'll reconsider the treatment of
massy, but until then it will be rare.