at the expense of someone Definition

expense
noun

1. The act of spending money, or the amount of money spent.

Thesaurus: fee, charge, cost, outlay, payment.
2. Something on which money is spent.
3. A sum of one's own money spent doing one's job, or this sum of money or an allowance paid by one's employer to make up for this.

Thesaurus: costs, overheads, outlay, incidentals.
Form: expenses

Idiom: at the expense of something or someone

With the loss or sacrifice of them.

Causing damage to their pride or reputation.
Example: a joke at my expense

With the cost paid by them.

Etymology: 14c: from Latin expensa, from expendere to weigh out.