Superheated liquid is a liquid which is not undergoing phase transition into gas in bulk (=boiling) even if its temperature is higher (that's why it is called superheated) than the temperature sufficient for this phase transition to occur (high enough temperature means high enough vapor pressure which can overcome external pressure). Superheated liquid is metastable state, a strong enough mechanical excitation or introduction of nucleation facilitators (dirt, radiation, charged particles) can destroy it and the phase transition then will occur.

Superheated liquid is a liquid which is not undergoing phase transition into gas in bulk (=boiling) even if its temperature is higher (that's why it is called superheated) than the minimum temperature necessary for this phase transition to occur (high enough temperature means high enough vapor pressure which can overcome external pressure). Superheated liquid is metastable state, a strong enough mechanical excitation or introduction of nucleation facilitators (dirt, radiation, charged particles) can destroy it and the phase transition then will occur.