IPA: /dɪsˈdeɪn.fəli/
KK: /dɪsˈdeɪn.fəl.i/
In a way that shows a lack of respect or consideration for someone or something.
She looked at him disdainfully when he suggested the idea.
**Disdainfully** → It is formed from "dis-" (meaning apart or away) and "dais" (from Old French *deis*, meaning to look down upon). The suffix "-fully" (meaning in a manner full of) indicates the manner of the action. Thus, "disdainfully" means in a manner that looks down upon or shows contempt.
Think of 'looking down upon' ('dais') someone 'apart' ('dis-') — that's why disdainfully means to do so in a contemptuous manner.