n. 1.a structure consisting of something wound in a continuous series of loops 2.a round shape formed by a series of concentric circles 3.a transformer that supplies high voltage to spark plugs in a gasoline engine 4.a contraceptive device placed inside a woman's womb 5.tubing that is wound in a spiral 6.reactor consisting of a spiral of insulated wire that introduces inductance into a circuit coil v. 1.to wind or move in a spiral course 2.make without a potter's wheel 3.wind around something in coils or loops