a large pipe or wire carrying the public supply of water, electricity, or gas:
The report found that many of Yorkshire's water mains needed replacing.
a burst gas main
2 British English
the place on a wall where you can connect something to a supply of electricity:
You can run the torch off batteries or plug it into the mains.
at the mains
Make sure that the television is turned off at the mains.
gas, water, or electricity supplied to a building through a pipe or wire:
The heater will run off mains gas or bottled gas.
Their job in the main consisted of cleaning and maintaining the building.