sponge bag noun2 •(UK, Australia) A bag for carrying toiletries, as when travelling. •(UK) Designating clothing (especially trousers) with a fine, faint black-and-white check pattern.In every hotel in Ireland sits a military man with […] a loud commanding voice, & spongebag coat & red slippers. — 1934 formssponge bags · sponge-bags · spongebags