Webster's Revised Unabridged Dictionary · 1913

Sienna

Sienna , noun

[Italian terra di Siena, from Siena in Italy.]

(Chemistry) 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.
Collocations (2)
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.