The word "umteenth" is an informal adjective used to denote a large number. It is often used to show exaggeration or emphasize a large amount. Some synonyms for the word include countless, innumerable, endless, myriad, and incalculable. These words are often used in place of "umteenth" to add additional emphasis to a statement about quantity. Other synonyms for "umteenth" include multiple, abundant, countless, infinite, and numerous. Using synonyms for "umteenth" can help writers and speakers accurately convey the magnitude of the amount they are referring to while also adding variety to their language.