A ball filled completely with air is said to be inflated. What do you say if a ball is in a 'not that much inflated' condition? Is there a single word for it? Are there other words that give the same meaning as that of inflated/'not so inflated'
I think Underinflated is what you are looking for.
If it had once been gas filled, it could be deflated
1 Having been emptied of air or gas.
‘a deflated balloon’