IPA: /kəmˈpliːtli/
KK: /kəmˈplitli/
In a way that is full or total; without anything left out.
She completely finished her homework before dinner.
Completely → It is formed from "com-" (meaning together or fully) and "pletere" (from Latin "plere", meaning to fill). The word "completely" means to fill something fully or entirely.
Think of 'fully' ('com-') filling something ('plere') — that's why completely means entirely.