A coil of rope or wire is a length of it that has been wound into a series of loops.

A coil is one loop in a series of loops.

A coil is a thick spiral of wire through which an electrical current passes.

In a vehicle, the coil is the part on a petrol engine that sends electricity to the spark plugs.

The coil is a contraceptive device used by women. It is fitted inside a woman's womb, usually for several months or years.

If you coil something, you wind it into a series of loops or into the shape of a ring. If it coils around something, it forms loops or a ring.