IPA: /ɪnˈdɛləbli/
KK: /ɪnˈdɛləbli/
In a way that cannot be removed, erased, or forgotten.
The artist's signature was indelibly marked on the painting.
Indelibly → It is formed from "in-" (meaning not) and "delere" (meaning to erase). The word "indelibly" means not able to be erased or removed, indicating a permanent mark or impression.
Think of something that cannot be 'erased' ('delere') — the 'in-' means not, so indelibly refers to something that is not able to be erased.