IPA: /ˈmɪstrʌstfəli/
KK: /ˈmɪstrʌstfəli/
In a way that shows doubt or lack of trust towards someone or something.
She looked at him mistrustfully, unsure of his intentions.
Mistrustfully → It is formed from "mis-" (meaning wrongly or badly) and "trust" (from Old French *troster*, meaning to rely on or have confidence in) and "-fully" (meaning in a manner). The word "mistrustfully" means in a manner that shows a lack of trust or confidence.
Think of 'mis-' meaning wrongly and 'trust' as relying on someone. When someone acts 'mistrustfully', they are showing a lack of confidence in others.