What does "serpentine" mean?

Serpentine: (Min.) A mineral or rock consisting chiefly of the hydrous silicate of magnesia. It is usually of an obscure green color, often with a spotted or mottled appearance resembling a serpent's skin. Precious, or noble, serpentine is translucent and of a rich oil-green color. Note: Serpentine has been largely produced by the alteration of other minerals, especially of chrysolite.