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

• propositional attitude
• propositional attitudes
• propositional calculus
• propositioned
• propositioning
• propositions
• propound
• propounded
• propounder
• propounders
• propounding
• propounds
• proppant
• proppants
• propped
• propping
• propraetor
• propraetorial
• propraetorian
• propraetors
• propranolol
• propranolols
• proprietaries
• proprietary
• proprietary chapel