noun
fallout; deposited matter
Technical term for particulate matter that settles from the atmosphere, especially radioactive fallout. Used in environmental and nuclear contexts.
原発事故後、降下物の調査が行われた。
After the nuclear accident, surveys of fallout were conducted.
降下物には放射性物質が含まれている可能性
Fallout may contain radioactive materials.
Compound of 降下 (こうか, 'falling, descent') and 物 (ぶつ, 'thing, matter').