Dreamt

Dreamt' is the only English word that ends with 'mt'

According to Oxford Dictionaries, 'dreamt' is the only English word that ends with 'mt'. The word's derivatives including undreamt, daydreamt, and redreamt are the only other words that end with the same letters. The term is a variant of 'dreamed', the past tense of the verb dream, and is commonly used in British English.