The Collaborative International Dictionary
Lawsonia alba
Henna \Hen"na\, n. [Ar. hinn[=a] alcanna ( Lawsonia inermis syn. Lawsonia alba). Cf. Alcanna, Alkanet, Orchanet.]
(Bot.) A thorny tree or shrub of the genus Lawsonia ( Lawsonia alba). The fragrant white blossoms are used by the Buddhists in religious ceremonies. The powdered leaves furnish a red coloring matter used in the East to stain the nails and fingers, the manes of horses, etc.
(Com.) The leaves of the henna plant, or a preparation or dyestuff made from them.