Meaning of FACTORIAL in English

FACTORIAL

fac ‧ to ‧ ri ‧ al /fækˈtɔːriəl/ BrE AmE noun [countable] technical

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

factorial 3 = 3 x 2 x 1

Longman Dictionary of Contemporary English.      Longman - Словарь современного английского языка.