Here’s some fun military slang dating back to 1919. “Umpty” (like “twenty“) and “umpteen” both meant “some amount that’s either unknown or enormous.”
“Umpteen” in particular has stuck around as a slangy word meaning “many, several, a whole bunch, or some large unknown amount.”
Part of speech:
Like other words for numbers and amounts, “umpteen” can be an adjective (“Why are there umpteen empty pizza boxes on the floor?”) as well as a noun (“They have umpteen of these;” “Apparently I broke Rule Umpteen“).
The adverb is “umpteenth,” as in “That’s my umpteenth robocall since lunch.”
how to use it:
The rare word “umpteen” gives you a slangy, silly way to emphasize just how many of something there are, especially in exasperation: “Ugh, I have umpteen more reports to write this week.” “That song is stuck in my head–sorry for singing the same line umpteen times.”
As you’ll see in the first example below, “umpteen” most often takes on a relaxed, conversational tone. But as the second example will show, “umpteen” can also inject some conversational color into an otherwise serious discussion.
And it can get dark! “Umpteen” can suggest that your exasperation has turned into bewilderment: that you’re so flummoxed by how long something is taking, how many times something has happened, or many things must be accomplished or considered that you’ve lost the ability to keep count of things. “When I’d heard the song for the umpteenth time, the lyrics had blurred into a meaningless chant.”
“I may not’ve had a date in umpteen years, but who does he think he is?”
— Kathryn Stockett, The Help, 2009
“You begin, while reading this volume, to fear nouns: They appear like links Mr. Leader is certain to click on and send himself down a rabbit hole. If the notion of motherhood comes into view, for example, we are off on how every mother has appeared in Bellow’s oeuvre… These umpteen detours — on assimilation, brothers, businessmen, Judaism, petty crime, you name it — pluck one from Bellow’s life for pages at a time.”
— Dwight Garner, New York Times, 28 April 2015