1. not suitable for breathing; lacking sufficient oxygen or containing harmful substances

Examples

• The air in the mine became unbreathable due to toxic gases.
• Smoke from the fire made the atmosphere unbreathable.
• At high altitudes, the thin air can feel unbreathable.
• The pollution in the city made the air nearly unbreathable.
• Emergency crews wore masks because the air was unbreathable.
• The sealed room quickly became hot and unbreathable.