Plain English Meaning

Flying into a thunderstorm by accident, when you didn't intend to and didn't see it coming in time to turn away.

Full Definition

An unintended entry of an aircraft into a thunderstorm or its associated severe weather, typically the result of being unable to see or detect the storm in time to avoid it, deteriorating conditions ahead of the aircraft, or being routed into embedded convective activity hidden within other clouds.

Context Anchor

Seen in instrument flying discussions about what to do if a pilot unexpectedly enters a thunderstorm.

Derivation

‘Inadvertent’ comes from the Latin ‘in-’ (not) and ‘advertere’ (to turn toward, to pay attention). It literally means ‘not turned toward’ — i.e., not done on purpose. ‘Penetration’ comes from Latin ‘penetrare’ (to enter, pass into). Together: entering something without meaning to.