to spend more money than you should

The council seems likely to overspend this year. 市政会今年可能会超支。

The hospital has already overspent (on) its budget. 医院开支已超过了预算。

an amount of extra money that is spent on something above the amount that should have been spent

We're expecting to have a $5 million (budget) overspend this year. 今年我们预计会超支500万美元。