umpteen - numerous
‘Umpteen’ is an informal term that is used to refer to a relatively large but unspecified amount. It is commonly followed by the word ‘time(s)’ and tends to be expressed when flustered or aggravated.
You need to be more switched on. I shouldn’t have to tell you to do something umpteen times!
I’ve left umpteen messages on the client’s phone, but she hasn’t called me back yet.
Person A: “Can I borrow your car?” Person B: “For the umpteenth time - no!”