Definitions

1. adjective

becoming or smelling more musty; stale and unpleasantly smelling

“The attic had become a mustier place after the flood.”

2. comparative

used to compare two things, indicating that one is more musty than the other

“This room is mustier than the one we left.”

3. superlative

used to compare three or more things, indicating that one is the most musty

“This house is the mustiest one on the street.”