1. [for something] to turn itself on. Exactly at midnight, the lights switched on. The radio switched on early in the morning to wake us up.
2.Sl. [for someone] to become alert or excited. The wild music made all the kids switch on and start to dance. About midnight, Ed switches on and becomes a real devil.
1. in. to come alive. She saw her child and immediately switched on.
2. in. to become modern and participate in current fads and events. Most kids I know switched on when they went to high school.
3. in. to get high on drugs; to begin taking LSD or some other hallucinogens. (see also turn on, switched on.) There was some old man who seemed to get pleasure from getting kids to switch on. Maybe he was a dealer.