Math. the product of a given series of consecutive whole numbers beginning with 1 and ending with the specified number: the factorial of 5 (5!) is 1 × 2 × 3 × 4 × 5, or 120
See factorial in American Heritage Dictionary 4
(făk-tôrˈē-əl, -tōrˈ-)
noun
The product of all the positive integers from 1 to a given number: 4 factorial, usually written 4!, is equal to 24 (1 × 2 × 3 × 4 = 24).