Refers to things that are left over or offered, especially food placed on a household altar (仏壇) as an offering, or more broadly, something that results from a process (yield) or is discarded (waste). The exact meaning depends on context.
We take down the food offerings from the Buddhist altar and eat them together.
The yield from this field was small this year.
We properly dispose of the waste from the construction work.
Compound of 上がり (agari, 'rising' or 'result', the continuative form of 上がる) and 物 (mono, 'thing'). The meaning 'food offering' comes from the idea of something that has been offered up (to the altar) and then taken down; 'yield' and 'waste' derive from the notion of something that results from a process.