Turn on Definition 1 of 5Pro Tip 1/3Physical Action Often involves physically interacting with a device or switch. Can you turn on the fan? It's hot in here. Pro Tip 2/3Common Places Used in homes, workplaces and places with electronic devices. Please turn on the lights when you enter the room. Pro Tip 3/3Start of Action Indicates the beginning of an action or operation. You need to turn on the machine to start printing.