Meaning of FACTORIAL in English

FACTORIAL

/ fækˈtɔːriəl; NAmE / noun

( mathematics ) the result when you multiply a whole number by all the numbers below it :

factorial 5 (represented as 5!) = 5 × 4 × 3 × 2 × 1

Oxford Advanced Learner's English Dictionary.      Оксфордский английский словарь для изучающик язык на продвинутом уровне.