the curve theoretically assumed by a perfectly flexible and inextensible cord of uniform density and cross section hanging freely from two fixed points
an imaginary great circle on the surface of the earth passing through the north and south poles at right angles to the equator; "all points on the same meridian have the same longitude"
a rigid circular band of metal or wood or other material used for holding or fastening or hanging or pulling; "there was still a rusty iron hoop for tying a horse"