Completely; wholly — especially used when something is entirely covered, buried, or enveloped.
雪ですっぽりと家が埋まってしまった。
The house was completely buried in snow.
帽子ですっぽり頭を隠したので、誰だか分からなかった。
He hid his head completely under a hat, so I couldn't tell who he was.
箱に入れて蓋をすると、中身がすっぽり収まる。
When you put it in the box and close the lid, the contents fit snugly.
Neatly; snugly; cleanly — used when something is inserted or removed smoothly and fits snugly or comes out cleanly.
指が指輪にすっぽり入ってしまった。
My finger slid completely into the ring.
棚に本がすっぽり収まって見た目がきれいだ。
The books fit neatly on the shelf and it looks tidy.
古いネジが外れて、部品がすっぽり抜け落ちた。
An old screw came off and the part slipped out cleanly.