adjective , noun
■ adjective
1.
able to be connected using a plug :
a plug-in kettle
2.
( computing ) able to be added to a computer system so that it can do more things :
a plug-in graphics card
■ noun
1.
( computing ) a piece of computer software that can be added to a system so that it can do more things
2.
( CanE ) a connection to an electricity supply in a garage, etc. so that you can use an electric heater to warm the engine of a car, so that it starts more easily