Definition

1. Adjective:
   • Not allowing air or gas to pass in or out: Describes a container, seal, or space that is completely closed, preventing the passage of air or other gases.
   • Having no weak points; impossible to disprove or weaken: Describes an argument, alibi, or plan that is so complete and well-constructed that it cannot be faulted or challenged.

Usage and Examples

• Literal meaning (sealing out air/gas):

  • Store the coffee in an airtight container to keep it fresh.
  • The submarine's hatch must be airtight to prevent water from entering.

• Figurative meaning (having no flaws):

  • The lawyer presented an airtight case, leaving no room for doubt.
  • We need an airtight plan before we proceed with the project.

Advanced Usage

• "airtight alibi": An alibi that is completely verifiable and impossible to contradict.
  • The suspect had an airtight alibi; he was recorded on camera in another city at the time of the crime.

Variants and Related Words

• Hermetic (adj): A more formal synonym for , especially in technical contexts. It can also imply secrecy or being sealed off from external influence.
  • The documents were kept in a hermetically sealed vault.

Synonyms

• Sealed: Closed securely.
• Watertight: Often used interchangeably in a figurative sense for arguments or plans, though it literally means impervious to water.
• Foolproof: So simple or well-designed that it cannot fail or be misused.

Antonyms

• Porous: Allowing liquid or air to pass through.
• Leaky: Having holes or cracks that allow substance to pass.
• Flawed: Having defects or weak points.

Related Phrases and Idioms

• "Locked down tight": An informal phrase meaning extremely secure or without loopholes, similar to the figurative use of .
  • The security for the event was locked down tight.

Adjective

1. not allowing air or gas to pass in or out
2. having no weak points
   • an airtight defense
   • an airtight argument