Thesaurus Weirdness

I looked up "umpteenth" in the online thesaurus, and not surprisingly it didn't recognize the word.  

It suggested I might be looking for some form of "impotent."

I found that to be rather an odd guess.  Perhaps it is just me. 

I'll keep playing on the interwebs, but if you happen to know of a word that has the same connotations as "umpteenth" but is a bit less modern-sounding, let me know.