IPA: /dʒuˈplɪsɪtəsli/
KK: /dʒuˈplɪsɪtəsli/
In a way that is deceitful or dishonest, often pretending to be something one is not.
He acted duplicitously, pretending to be a friend while secretly undermining her.
Duplicitously → It is formed from "duplic-" (from Latin "duplicare", meaning to double) and "-ous" (meaning full of) and "-ly" (meaning in a manner). The word describes behaving in a manner that is full of double-dealing or deceit.
Think of 'double' ('duplic-') to remember that 'duplicitously' means behaving in a deceitful or double-dealing way.