A useful or usable thing. Often used in negative expressions such as 'not fit for use'.
古いパソコンは動きが遅くて、もう使い物にならない。
The old PC is slow and is no longer of any use.
壊れた工具は現場では使い物にならないので交換した。
Broken tools were no use on site, so we replaced them.
曇りで天体望遠鏡は使い物にならなかった。
It was cloudy so the telescope was no use.
A present or gift in some usages (a somewhat old-fashioned or dialectal meaning). Context determines this meaning.
お世話になった隣人に使い物を持って行った。
I brought a small gift to the neighbor who helped me out.
子どもが作った花束を先生への使い物として渡した。
The child gave a bouquet they made to the teacher as a present.