factorial/fækˈtɔ:rɪəl; fæk`tɔrɪəl/ adj, n (mathematics 数) (of the) product of a whole number and all those whole numbers below it 阶乘; 阶乘的; 因数的 factorial 5 (represented as 5!), ie the product of 54 32 15的阶乘（记作5!, 为54321的乘积）.
牛津英汉双解词典