at (one's) expense

1. Something spent to attain a goal or accomplish a purpose: an expense of time and energy on the project.

2. A loss for the sake of something gained; a sacrifice: achieved speed at the expense of accuracy.

3. Charges incurred by an employee in the performance of work: was reimbursed for her travel expenses.

4. Informal Money allotted for payment of such charges.

An expenditure of money; a cost: an improvement that was well worth the expense; a trip with all expenses paid.

expenses

1. Charges incurred by an employee in the performance of work: was reimbursed for her travel expenses.

2. Informal Money allotted for payment of such charges.

Something requiring the expenditure of money: Redecorating the house will be a considerable expense.

Archaic The act of expending.

To charge with expenses.

To write off as an expense.