asymmetrical spinnaker

Short definition from Wiktionary

Noun

1. 1
   A headsail which, like ordinary spinnaker is attached to the boat only in its corners, but is asymmetrically shaped. The shape makes is suitable for winds from beam reach to broad reach whereas ordinary symmetrical spinnaker is best suited for winds from run to broad reach. The tack of the asymmetrical spinnaker is usually attached to a bowsprit instead of a spinnaker pole.