1. the boss of a shield, especially the round projection at the center
Usage: historical; military
2. a rounded knob or projection
Usage: technical
3. the beak of a bivalve shell
Usage: biology

Examples

• The ancient warrior’s shield featured an iron umbo at its center.
• Roman shields were reinforced with a metal umbo for both protection and offense.
• The archaeologist identified the shield fragment by its distinctive umbo.
• The door handle had a decorative umbo that caught the light.
• Marine biologists examine the umbo to determine the age of the clam.
• The umbo of the mussel shell showed signs of wear from the rocky substrate.