Pith helmet
WordNet
noun
(1) A lightweight hat worn in tropical countries for protection from the sun
WiktionaryText
Noun
- 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. Originally used by the British army in India in the 19th century, later used more widely.
- A hat of similar appearance, but made of different materials.