pith helmet

pith helmet (plural pith helmets)

1. A lightweight helmet-shaped hat made of the pith of the sola or shola (Indian spongewood) plant covered with white cotton and faced with green cloth. Also known as a "sola topi", it was originally used by the British army in India in the 19th century, later used more widely.
2. A hat of similar appearance, but made of different materials.

• topee, sola topi, solar topee