IPA: /fərˈɡɛtfəli/
KK: /fərˈɡɛtfəli/
In a way that shows a lack of memory or attention, often leading to forgetting things.
She forgetfully left her keys on the table again.
Forgetfully → It is formed from "forget" (from Old English *forgietan*, meaning to lose memory of) and "-fully" (meaning in a manner full of). The word "forgetfully" means in a manner full of forgetting or not remembering.
Think of losing memory ('forgietan') and doing so 'fully' — that's why forgetfully means acting in a way that shows you are not remembering.