(informal) to stop thinking about something or paying attention to something When I hear the word ‘football’ I switch off (= because I am not interested in it). The only time he really switches off (= stops thinking about work, etc.) is when we're on vacation.
to turn a light, machine, etc. off/on by pressing a button or switch Please switch the lights off as you leave. How do you switch this thing on? The electricity has been switched off. We only switched on halfway through the programme. See related entries: How machines work