The Collaborative International Dictionary of English v.0.48:
Twelve \Twelve\, n. 1. The number next following eleven; the sum of ten and two, or of twice six; twelve units or objects; a dozen. [1913 Webster] 2. A symbol representing twelve units, as 12, or xii. [1913 Webster] The Twelve (Script.), the twelve apostles. --Matt. xxvi. 20. [1913 Webster]