Informal Relatively large but unspecified in number: umpteen reasons; umpteen guests. (adjective)
American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Use "umpteen" in a sentence
"LäraBars come in umpteen flavors and also have a chocolate bar counterpart, Jŏcalat."
"That's the first in umpteen decisions to make, before reaching the end."
"Or it might be an indication that Web companies are making the same "invest in umpteen businesses" mistake which leads to big losses when recession hits."