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.