As adjectives the difference between mastless and massless
is that mastless is without a mast while massless is having no mass.
mastless
English
Adjective
(
-)
Without a mast.
- a mastless ship
Bearing no mast (fruit of a tree).
- a mastless oak or beech
- (Dryden)
massless
English
Adjective
(
-)
Having no mass.
-