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1. To activate, connect, or start the function of something, with or as with a power switch. In this usage, a noun or pronoun can be used between "switch" and "on." Would you switch on the water heater for me, please? I need to switch on the lights to see properly. Make sure you have the car in neutral before you switch it on.
2. To activate or begin functioning automatically or as if automatically. The computer switches on as soon as you wiggle the mouse. We've set the lights to switch on at 8 PM every evening while we're on vacation so people don't know the house is empty.
3. To become animated, lively, and alert, especially suddenly or on short notice. Tom was a bit at the start of dinner, but he switched on after he'd had a couple of drinks. She's such a quiet, reserved woman most of the time, but she really switches on when we all go out for dancing on the weekends.
4. To begin exuding or producing something as if connected to a power supply. Toddlers know how to switch on the cuteness after being naughty so they don't get in as much trouble. I don't have as many qualifications as some of the other applicants, so I'll definitely have to switch on the charm during the interview.
switch something on
to close an electrical circuit that causes something to start functioning or operating. Please switch the fan on. I switched on the fan.
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. Sl. alert and up-to-date; with it. My brother is switched on and has lots of friends. I'm not switched on. In fact, I am pretty dull.
2. Sl. excited. I get switched on by that kind of music. I am never switched on by raucous music.
Produce as if operating by a control, as in She switched on the charm as soon as he walked in. [Mid-1900s] Also see switch off.
To activate something using a switch: We switched on the lights and entered the room. I switched the fan on to cool down the kitchen.
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.
1. mod. alert and up-to-date; with it. My brother is switched on and has lots of friends.
2. mod. excited. I am never switched on by raucous music.