1. the bottom or lower surfaces of objects
Usage: plural form of underside

Examples

• The undersides of the leaves were covered with tiny insects.
• Check the undersides of your shoes for mud before entering.
• The mechanic examined the undersides of both vehicles.
• Birds often have different colored feathers on their undersides.
• The undersides of the bridge showed signs of rust.
• She painted the undersides of the shelves white.
• The undersides of mushrooms contain their spores.