umbo /umˈbō/

1. The central boss of a shield
2. A knob
3. The protuberant oldest part of a bivalve shell
4. A knob on a toadstool cap
5. A projection on the inner surface of the eardrum where the malleus is attached

umˈbonal /-bən-əl/ adjective

• ride herd on
• rident
• ride off
• ride on
• ride out
• rider
• ridered
• riderless
• ride roughshod over
• riders
• rides
• ride shotgun
• ride someone off
• ride the beam
• ride the rods
• ride the Spanish mare
• ride to hounds
• ride up
• ridge
• ridgeback
• ridgebacks
• ridge bone
• ridge bones
• ridged
• ridgel