turn on

(verb): To set a flow of fluid or gas running by rotating a tap or valve.
(verb): To power up, to put into operation, to start, to activate (an appliance, light, mechanism, functionality etc.).
(verb): (of a device) To start operating; to power up, to become on.
(verb): To fill with enthusiasm; to intoxicate, give pleasure to ( + to an object of interest or excitement).
(verb): To sexually arouse.
(verb): To cause to take up drugs, especially hallucinogens.
(verb): To violently rebel against; to suddenly attack (this is the intransitive verb turn, with on functioning as a preposition not as an adverbial particle).
(verb): To depend upon; to pivot around, to have as a central subject (this is the intransitive verb turn, with on functioning as a preposition not as an adverbial particle).