stubbornly
US /ˈstʌb.ɚn.li/
UK /ˈstʌb.ɚn.li/

1.
koppig, hardnekkig
in a determined way, especially by refusing to change your mind or be persuaded, even when it would be more sensible to do so
:
•
He stubbornly refused to admit he was wrong.
Hij weigerde koppig toe te geven dat hij ongelijk had.
•
The old door stubbornly resisted all attempts to open it.
De oude deur verzette zich koppig tegen alle pogingen om hem te openen.