Definition of "synthesizer"

(music) An electronic instrument that creates its sounds with electronics and generally is played via a keyboard.  examples

(music) An electronic instrument consisting of a module, or a set of modules, that creates its sounds with electronics and does not have any keyboard.  examples

(electronics) An electronic circuit that generates an electronic signal oscillation with accurate timing from a reference oscillator.  examples

(electronics) An electronic device that generates electronic signal patterns to test an electronic circuit.  examples

(software) A software program that allows a computer to be used as a musical instrument – virtual instrument  examples