B2 [U] the use of money, time, or effort: Buying a bigger car has proved to be well worth the expense. We've just had a new garage built at great expense. We went on holiday at my father's expense (= he paid for it). It's silly to go to the expense of (= spend money on) buying new clothes when you don't really need them.Costs and expenses › [C] something that makes you spend money: Our biggest expense this year was our summer holiday. We need to cut down on our expenses.Costs and expenses expenses C1 [plural] › money that you spend when you are doing your job, that your employer will pay back to you: I need to get my expenses approved.UK Don't worry about the cost of lunch - it's on expenses.Costs and expenses