flying two jibs simultaneously, one in each slot of a dual-grooved head foil (e.g., Tuff Luff) or with their hanks interleaved. One jib is sheeted to the boom’s aft end; a spinnaker or whisker pole holds out the other. Used for better performance downwind when a boat is too shorthanded to use a spinnaker. An illegal racing configuration. Also referred to as a butterfly. Compare to: double-headed.