← BackshareGuessfatheadedly/ˈfætˌhɛdɪdli/adverbIn a stupid, foolish, or stubborn manner.He fatheadedly refused to wear a helmet while biking.She fatheadedly spent all her money on lottery tickets.They fatheadedly ignored the safety instructions.SynonymsfoolishlystupidlyAntonymssensiblywisely