IPA: /ɪnˈtaɪərli/
KK: /ɪnˈtaɪərli/
Completely or fully; without any part left out.
She was entirely focused on her studies during the exam period.
Entirely → It is formed from "entire" (from Old French *entier*, meaning whole or complete) and the suffix "-ly" (meaning in a manner of). The word "entirely" means in a manner that is whole or complete.
Think of something being 'whole' ('entire') and the '-ly' indicating how it is done. So, when something is done entirely, it is done in a complete manner.