noun
extra income; windfall; incidental earnings
Refers to money received unexpectedly or outside one's regular salary, such as a bonus, gift, or one-time payment. Often used in personal finance contexts.
今月は臨時収入があったので、少し贅沢をしようと思う。
I had some extra income this month, so I'm thinking of splurging a little.
臨時収入が入ったら、まず貯金に回すようにしている。
Whenever I get a windfall, I make it a rule to put it into savings first.