Wiring is all the wires inside a building, a car, or a machine, taken together as one system — the electric veins hidden behind the walls and under the floor. Because it names the whole set and not the separate pieces, it is uncountable: say the wiring, some wiring, a lot of wiring, and never a wiring or two wirings. If you need to count, count the wires or the cables. It is the word people use when something is wrong or when work is being done: The wiring in this old house needs replacing. There must be a fault in the wiring. An electrician rewires a house, and after the job you talk about the new wiring. Two more uses are worth knowing. First, wiring is also the -ing form of the verb wire, so it can name the act of putting the wires in: Wiring the whole flat took three days. Second, people use it about the brain and about human nature — It's just how he's wired, meaning that is his built-in character, not something he chose. Both of these are common and natural.