Rambutan \Ram*bu"tan\, n. [Malay ramb[=u]tan, fr. rambut hair of the head.] (Bot.) A Malayan fruit produced by the tree {Nephelium lappaceum}, and closely related to the litchi nut. It is bright red, oval in shape, covered with coarse hairs (whence the name), and contains a pleasant acid pulp. Called also {ramboostan}.