flummox /flumˈəks/ (informal)

To perplex or puzzle

• invalid
• invalidate
• invalidated
• invalidates
• invalidating
• invalidation
• invalidations
• invalided
• invalidhood
• invalidhoods
• invaliding
• invalidings
• invalidism
• invalidisms
• invalidities
• invalidity
• invalidly
• invalidness
• invalidnesses
• invalids
• invaluable
• invaluableness
• invaluably
• Invar
• invariabilities