1. the umbrella-shaped cap of a mushroom or other fungus
Usage: botanical
2. a brimless cap worn in ancient Rome
Usage: historical

Examples

• The pileus of the mushroom was bright red with white spots.
• Scientists examined the pileus to identify the fungus species.
• The pileus expanded as the mushroom matured.
• Ancient Roman slaves wore a pileus as a symbol of freedom.
• The botanist measured the diameter of each pileus.
• A pileus can vary greatly in color and texture between species.