plug in
• connect an electrical appliance to the mains by inserting a plug in a socket.
• "she plugged in the electric kettle and spooned coffee into the percolator"
plug-in
adjective
• able to be connected by means of a plug.
• "a plug-in kettle"
plug-in
noun
• a plug-in module or plug-in software.
• an electric socket in a car park or garage for plugging in the block heater of a vehicle to prevent the engine from freezing.
