noun
A spongy, lightweight rubber material made by foaming; used in cushions, mattresses, insulation, and similar products.
このクッションには発泡ゴムが使われている。
This cushion uses foam rubber.
スポンジゴム is also a spongy rubber, but often refers to a more open-cell, absorbent structure, while 発泡ゴム typically implies a closed-cell foam.
Compound of 発泡 (foaming) and ゴム (rubber, from Dutch 'gom').