Armstrong limit
the altitude above which water boils at human body temperature, making it absolutely impossible for humans to survive unpressurized; approx. 18–19 km above sea level
en-US/ˈɑɹmˌstɹɑŋ ˈlɪmət/
en-GB/ɑːmstɹɒŋ ˈlɪmɪt/
the altitude above which water boils at human body temperature, making it absolutely impossible for humans to survive unpressurized; approx. 18–19 km above sea level