meaning in context - What does "expense" mean in "we all had a meal at the airline's expense"?

I'm reading a book which states the following sentence:

When our flight was delayed, we all had a meal at the airline's expense.

I've tried to find in the following dictionary the definition of the word expense in this context but I'm not sure which one of them is the right.

To which definition in the following dictionary is matched? Dictionary.com: expense

Answer

I'm not entirely happy with the entries given in the link.

1. at someone's expense
   
   Paid for by someone.
   ‘the document was printed at the taxpayer's expense’
   1.1 With someone as the victim, especially of a joke.
   ‘my friends all had a good laugh at my expense’

So in OP's example, the airline paid for "our" meals. In other words, the meals were free to compensate "us" for the delay.