/'ʌmpti:nθ; `ʌmp`tinθ/
pron, det
*For the umpteenth time, I tell you I don't know! 我告诉你多少次了, 我不知道!

adj [only before noun]
[Date: 1900-2000; Origin: umpty 'many' (a joke word) (1900-2000) + -teenth (as in thirteenth)]
if something happens for the umpteenth time, it happens again after having happened many times before - used when you are annoyed that it has happened so often
　'This is crazy,' she told herself for the umpteenth time .