/plug"in'/ , adj.
1. capable of or designed for being connected to an electrical power source by plugging in or inserting: a plug-in hair dryer; a plug-in transistor.
n.
2. plug (def. 3).
3. jack 1 (def. 3).
4. a plug-in appliance.
[ 1920-25; adj., n. use of v. phrase plug in ]