noun
self-inflating type; automatic inflation type
Used as a noun or noun modifier for devices that inflate automatically, such as life jackets or air mattresses.
この救命胴衣は自動膨張式です。
This life jacket is the self-inflating type.
自動膨張式のエアマットを買った。
I bought a self-inflating air mattress.
Compound of 自動 (automatic) + 膨張 (inflation) + 式 (type/style).