An uncountable or indefinitely large number of times. The word umpteen is an American coinage that was believed, by John Ciardi and several other writers, to have come from nineteenth-century Morse code. In an early version of the code, M, pronounced “umpty,” meant “many,” probably based on M, the Roman numeral for one thousand. To this was added “teen,” for “ten,” presumably now meaning tens of thousands or, simply, a very large number. The expression “for the umpteenth time,” usually pronounced with some exasperation, means in effect that one has said or done something time and again and is thoroughly tired of the repetition.