Plug

—1. A terminal, consisting of a metal tip and sleeve, insulated from each other, and connected to a flexible cord, for inserting into a spring jack in a telephone switchboard, and making the desired connection. 2. A metal key with insulated handle for inserting between contact blocks te complete a circuit, as in a resistance box. s $ 3. A general term for a piece of any suitable material or form used to fill up a hole, the object usually being to prevent leaks.