Definition of mass:

part of speech: noun

The celebration of the Eucharist in the R. Cath. Ch.; the sacrifice of the mass, or the celebration of the Lord's Supper in the R. Cath. Ch.; high mass, that which is sung or chanted, low mass being only read.

part of speech: verb

To form into a mass; to form into a collective body; to assemble.

part of speech: noun

A body or lump; a large quantity; a heap; the quantity of matter in any body.