Si*en"na (?), n. [It. terra di Siena, fr. Siena in Italy.] Chem.
Clay that is colored red or brown by the oxides of iron or manganese, and used as a pigment. It is used either in the raw state or burnt.
Burnt sienna, sienna made of a much redder color by the action of fire. -- Raw sienna, sienna in its natural state, of a transparent yellowish brown color.
© Webster 1913.