electrical device that fits into the cylinder head of an internal-combustion engine and ignites the gas by means of an electric spark
"The mechanic replaced the old plug in the cylinder because it had failed to ignite the fuel mixture, causing the car to misfire."
an upright hydrant for drawing water to use in fighting a fire
"The firefighters quickly attached their hoses to the large metal plug on the side of the building to extinguish the blaze."
A pronged connecting device which fits into a mating socket, especially an electrical one.
"I need to find a spare plug for my phone charger since I left mine at home."
In plain English: A plug is a small piece of plastic that goes into an electrical outlet to let you use a device.
"I need to find an electrical plug for my new phone charger."
Usage: Use "plug" to refer to the physical connector inserted into a wall socket or appliance port to establish an electrical connection. Do not use it for the act of plugging something in, as that requires the verb form.
make a plug for; praise the qualities or in order to sell or promote
"Before we start the concert, I'll have to do a quick plug for our new merchandise line to help boost sales."
To stop with a plug; to make tight by stopping a hole.
"The plumber managed to stop the leaky pipe by plugging the hole with a wet rag before calling for professional help."
In plain English: To plug something means to fill a hole or opening with an object so that nothing can get through it.
"She plugged the headphones into her phone to listen to music."
Usage: Use "plug" as a verb to describe physically blocking an opening or gap, such as stopping a hole in a pipe with a cork or sealing a leak. Do not use it for connecting electronic devices, which is a separate meaning related to inserting a connector into a socket.
The word "plug" comes from Middle Dutch plugge, meaning "peg," and likely entered English via Northern Continental West Germanic roots. Its ultimate origin remains uncertain, though it may share a source with the Dutch word for a cut-out sod of earth.