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"
the process of ionizing; the formation of ions by separating atoms or molecules or radicals or by adding or subtracting electrons from atoms by strong electric fields in a gas
the condition of being dissociated into ions (as by heat or radiation or chemical reaction or electrical discharge); "the ionization of a gas"