2. (Mech.) (a) An instrument or contrivance to size articles, or to determine their size by a standard, or to separate and distribute them according to size. (b) An instrument or tool for bringing anything to an exact size. [ 1913 Webster ]
(n) (music) an electronic instrument (usually played with a keyboard) that generates and modifies sounds electronically and can imitate a variety of other musical instruments, Syn. synthesiser