Real Dictionary

coil
countable noun: A coil is one loop in a series of loops.
countable noun: A coil of rope or wire is a length of it that has been wound into a series of loops.

coil in American English 1
anything wound or gathered into a series of rings or a spiral
to wind around and around
to wind or gather (rope, a hose, etc.) into a circular or spiral form
intransitive verb: to form rings, spirals, etc.; gather or retract in a circular way
noun: a connected series of spirals or rings into which a rope or the like is wound
transitive verb: to wind into continuous, regularly spaced rings one above the other

coil in American English 2
commotion; turmoil
noun: a noisy disturbance; commotion; tumult

coil in British English 1
noun: something wound in a connected series of loops
verb: to wind or gather (ropes, hair, etc) into loops or (of rope, hair, etc) to be formed in such loops

coil in British English 2
noun: the troubles and activities of the world (in the Shakespearean phrase this mortal coil)

coil in Chemical Engineering
noun: A coil is a twisted tube for carrying a fluid, which is used inside a vessel but has entry and exit points outside the vessel.

coil in Electrical Engineering
noun: A coil consists of several loops of conductor that may be round a central ferrous core.