floating object; driftage
Refers to something drifting in water, such as debris, a log, or a lost item carried by a current.
川に流れ物が浮かんでいる。
There is something floating in the river.
forfeited pawned article
Pawnbroker term for an item that was not redeemed and became the shop's property. Rare outside this domain.
質屋で流れ物を安く買った。
I bought a forfeited pawned item cheaply at the pawnshop.
Compound of 流れ (nagare, 'flowing') + 物 (mono, 'thing'). The pawnbroker sense derives from the idea of an item 'flowing away' from the original owner.