ichidan verb
Describes something suddenly slipping out of a grip, socket, or fitting, often with a popping sensation.
手が滑って、スマホがすっぽ抜けた。
My hand slipped and the smartphone popped out of my grip.
プラグがコンセントからすっぽ抜けている。
The plug has come loose from the outlet.
ichidan verb
completely forget; slip one's mind
Used when something is entirely forgotten, as if it has slipped out of one's memory. Often with 頭から or 記憶から.
約束が頭からすっぽ抜けていた。
The appointment had completely slipped my mind.