Umpteen reasons; umpteen guests.
She's taking umpteen friends with her to the party.
Origin of umpteen
- Slang ump(ty) dash in Morse code (of imitative origin) -teen (as in thirteen)
From American Heritage Dictionary of the English Language, 5th Edition
- umpty (“colloquial name for the dash ""”" in Morse code") +"Ž -teen