Expresses a bit of irritation or exasperation about repeated actions or situations. For the umpteenth time, stop leaving your toys on the floor!
Pro Tip 2/3
Informal Usage
Best used in casual conversation; it can seem out of place in formal writing or speeches. I've seen this movie for the umpteenth time and still love it.
Pro Tip 3/3
Not Literal
It doesn't mean a specific number, rather it indicates an unspecified, large number. I've been to this café umpteen times this month.