A gennaker is a sail that was developed around 1990. Used when sailing downwind, it is a cross between a genoa and a spinnaker. It is not symmetric like a true spinnaker but is asymmetric like a genoa, but the gennaker is not attached to the forestay like a jib or genoa. The gennaker is rigged like a spinnaker but the tack is fastened to the hull ... Found on http://en.wikipedia.org/wiki/Gennaker