* An ‘existential threat’ typically refers to an event that could kill either all human life, or all life in general.
That describes an extinction risk, which is one type of existential risk, but not the only type. Here are two of the most prominent definitions of existential risk:
An existential risk is one that threatens the premature extinction of Earth-originating intelligent life or the permanent and drastic destruction of its potential for desirable future development (Bostrom, emphasis added)
And:
An existential risk is a risk that threatens the destruction of humanity’s longterm potential. (Ord, The Precipice, emphasis added)
(See here for more details. And here for definitions of “global catastrophic risks”.)
(Just a tangential clarification) You write:
That describes an extinction risk, which is one type of existential risk, but not the only type. Here are two of the most prominent definitions of existential risk:
And:
(See here for more details. And here for definitions of “global catastrophic risks”.)