a big ask
An inconvenient request. I know it's a big ask, but could I borrow your car for a week?
a big ask
If you describe something that someone has asked you to do as a big ask, you mean that it will be difficult to do. It's a pretty big ask to run faster in the second half of the race. Two hours without a comfort break was a big ask for many.
a big ask
a difficult demand to fulfil. informal