IPA: /ˌɪn.dɛl.ɪˈbɪl.ɪ.ti/
KK: /ɪnˈdɛlɪbɪlɪti/
The quality of being impossible to remove or forget; something that cannot be erased or changed.
The indelibility of her memories made it hard for her to move on.
Indelibility is formed from "in-" (meaning not) and "delere" (meaning to destroy or erase) combined with the suffix "-ibility" (meaning the quality of being). The word refers to the quality of being unable to be erased or destroyed.
Think of 'not' ('in-') being able to 'erase' ('delere') something — that's why indelibility means something that cannot be erased.