(1):

(n.) The highly perfumed yellowish heartwood of an East Indian and Polynesian tree (Santalum album), and of several other trees of the same genus, as the Hawaiian Santalum Freycinetianum and S. pyrularium, the Australian S. latifolium, etc. The name is extended to several other kinds of fragrant wood.

(2):

(n.) The red wood of a kind of buckthorn, used in Russia for dyeing leather (Rhamnus Dahuricus).

(3):

(n.) Any tree of the genus Santalum, or a tree which yields sandalwood.