Completely Naked, Totally Naked, Completely Nude
noun, の adjective
You're all naked, which makes you completely naked or totally naked.
ぜんら
This is a jukugo word that uses the on'yomi readings of the kanji. You should be able to read this on your own.
一度しかない人生だろ！なぁ！一緒に全裸でスカイダイビングしに行こうぜ。すんげぇいい経験になると思うんだよね。
You only live once! Come on. You should go skydiving nude with me. It would be a great experience for us.