v.1. To deactivate something using a switch: We switched off the lights before we left the house. Switch that vacuum cleaner off so you can hear what I'm saying.
2. To stop paying attention; lose interest: The whole class switched off when the professor started talking about accounting.
3. To alternate performing some task with another person: We switch off the baby-sitting every Friday so that one of us can go to the movies. It's a long drive, but if we switch off we won't get tired.