Definition of umpteenth in US English:

umpteenth

ordinal number

informal
  • Used to emphasize that something has happened on many other occasions.

    ‘she checked her watch for the umpteenth time’
    ‘Totti swung his umpteenth corner into Scotland's box’
    • ‘After the umpteenth false start and the gazillionth freaky camera angle, it becomes apparent there's time to nap between things that happen that mean something.’
    • ‘Pity John Williams writing his umpteenth Star Wars score.’
    • ‘Microsoft's latest offering is the umpteenth overhaul of MSN, which has been bleeding money for eight years.’
    • ‘Blade doesn't have a sense of humour and after the umpteenth battle, you wish he had.’
    • ‘Everything you need to know about him is neatly encapsulated in the photographs that cover the sleeve of his umpteenth album.’

Pronunciation

umpteenth

/ˌəm(p)ˈtēnTH//ˌəm(p)ˈtinθ/