Leakproof

Built so that liquid or gas cannot escape through its enclosure.

Reach for it when describing a verified containment feature, not a casual hope that a vessel will hold

Each leakproof container kept the medical samples secure during transport.

• everyday

  spillproof

  ordinary tipping should not release the contents

  not when Spillproof may tolerate seepage and is a weaker claim than leakproof.

• everyday

  watertight

  the barrier specifically excludes or contains water

  not when Watertight does not guarantee containment of oil, vapor, or pressurized gas.

• professional

  airtight

  air exchange must be prevented

  not when An airtight enclosure is not automatically safe for every liquid or chemical.

• professional

  sealed

  an opening or joint has been securely closed

  not when A sealed package may still leak if its material or seam fails.

• formal

  impermeable

  the material itself does not let a substance pass

  not when Impermeability says little about lids, valves, and assembled joints.

• formal

  leak-resistant

  reduced likelihood is supported but absolute prevention is not

  not when Leak-resistant deliberately stops short of the full leakproof claim.

• leaky
• permeable
• unsealed

• leakproof container

  A leakproof container protected the dry food through the river crossing.

• leakproof seal

  The technician checked every leakproof seal before opening the valve.

• fully leakproof

  Testing confirmed that the bottle remained fully leakproof after repeated drops.