IPA: /hɑːrdˈhɛdɪdli/
KK: /hɑrdˈhɛdɪdli/
In a way that shows stubbornness or a refusal to change one's mind, often despite evidence or reason.
She hardheadedly refused to listen to any advice, believing she was right.
Hardheadedly → It is formed from "hard" (from Old English "heard", meaning firm or solid), "headed" (from "head", meaning the top or leader), and "-ly" (a suffix meaning in a manner of). The word "hardheadedly" means in a manner that is firm or stubborn, often refusing to change one's mind.
Think of being 'firm' ('hard') and 'leading' ('headed') in your decisions — that's why acting 'hardheadedly' means being stubborn.