slumberinggerund / present participle Used as a participial adjective; more precise than generic ADJECTIVE.
The slumbering cat lay peacefully on the windowsill.
Дремлющий кот мирно лежал на подоконнике.
The slumbering volcano hasn't erupted in centuries.
Спящий вулкан не извергался веками.
Gerundial use referring to the act or state of sleeping.