A word that usually prescribes an uncertain number of occurances. This is usually said in the reference of the numbers 13-19 (hence the 'teen'), but it can be in reference to any number within reason.
I got umpteen calls from this pranker yesterday.
I dyed my hair for the umpteenth time today.
An expression which denotes an abundance, large quantity, huge amount or a load of something. The word "umpteenth" was derived from "umpteen" and means "for-God-knows-which-time".
There was an umpteen of fidgety tourists in the city endeavouring to do as much sightseeing as it was possible.