n. (绘画等用的)底料, 石膏粉

[ noun ]
gypsum or plaster of Paris spread on a surface to make it suitable for painting or gilding (or a surface so prepared)
<noun.substance>

Gesso \Ges"so\, n. [It., chalk, plaster.]
1. Plaster of Paris, or gypsum, esp. as prepared for use in
painting, or in making bas-reliefs and the like; by
extension, a plasterlike or pasty material spread upon a
surface to fit it for painting or gilding, or a surface so
prepared.
[Webster 1913 Suppl.]

2. A work of art done in gesso. [Obs.]
[Webster 1913 Suppl.]