airtight

Everyday

1. Airtight means sealed so tightly that no air can get in or out. tree →
2. (figurative) An airtight argument, alibi or case has no weak points and cannot be proved wrong. tree →

In the lessons

In everyday life airtight boxes and jars keep food fresh and stop it going stale or mouldy. In science lessons airtight containers show that things need air (oxygen) to burn or rot, and help in experiments with gases. In detective stories an airtight alibi proves a suspect could not have done the crime. Phrases: airtight container, airtight seal, airtight alibi.

Examples

• Keep the biscuits in an airtight tin so they stay crunchy. tree →
• The jar has an airtight lid. tree →
• Without air, the candle in the airtight jar went out. tree →
• Astronauts' spacesuits must be airtight. tree →
• Never play inside an airtight box or old fridge — you could not breathe. tree →
• The detective could not arrest him because his alibi was airtight. tree →
• Her argument was airtight; nobody could find a flaw. tree →
• Then Oz painted it on the inside with a coat of thin glue, to make it airtight, after which he announced that the balloon was ready. tree →

Note

Written as one word: airtight. Similar: watertight (no water gets in). Safety: never close a person or pet inside an airtight space.