1. Keenly aware of and responsive to what is new and fashionable; hip
2. After you have changed the controls of an electrical or mechanical device to make it start producing or doing something, it is turned on. Turned off is the opposite of turned on. Switched on is similar to turned on.
3. When something about a person of the opposite sex causes you to become sexually or romantically interested in that person, you are turned on. Turned off is the opposite of turned on.