n.a reddish brown dye used especially on hairv.apply henna to one's hair
"She hennas her hair every month"
英汉双解大词典
henna/ˈhɛnə/
1.
N-UNCOUNT（不可数名词） Henna is a reddish brown dye that is made from the leaves of a shrub. It is used especially for colouring hair or skin. 散沫花染剂; 用于染发或涂饰皮肤