Related Clues:

• Irrefutable
• Impenetrable
• Unassailable, as an alibi
• Sealed
• Perfect, as an alibi
• Airtight
• Like good alibis
• Like a good alibi
• Hermetic
• Unbreakable, as a contract
• Unbreakable, as an alibi
• Solid, alibiwise
• Like an inflexible agreement
• Like perfect alibis
• Unbreakable