noun
Refers to the state of being completely naked, often used in expressions like 真っ裸になる or 真っ裸で.
彼は真っ裸で部屋を走り回った。
He ran around the room stark naked.
na-adjective, noun which may take the genitive case particle 'no'
Used adjectivally to describe someone or something as completely naked, with no clothes at all.
真っ裸の赤ちゃんがお風呂に入っている。
A stark naked baby is in the bath.