IPA: //ˈpɛnəˌtreɪtɪŋli//
KK: /ˈpɛnəˌtreɪtɪŋli/
In a way that is able to reach deeply into something or to understand something thoroughly.
She looked at him penetratingly, as if trying to see into his soul.
Penetratingly → It is formed from "penetrating" (from Latin "penetrare", meaning to enter or pierce) and the suffix "-ly" (meaning in a manner of). The word "penetratingly" means in a manner that enters deeply or pierces through.
Think of something that 'pierces' or 'enters deeply' ('penetrare') and how it is done 'in a manner' ('-ly'). This helps you remember that 'penetratingly' describes a way of going deep into something.