IPA: /frʌsˈtreɪtɪŋli/
KK: /frʌsˈtreɪtɪŋli/
In a way that makes someone feel annoyed or upset because they cannot achieve what they want.
She frustratingly tried to explain her point, but no one was listening.
Frustratingly → It is formed from "frustrate" (from Latin "frustrari", meaning to deceive or disappoint) and the suffix "-ingly" (meaning in a manner that). The word "frustratingly" describes an action done in a manner that causes disappointment or annoyance.
Think of the word 'frustrate' which means to disappoint, and remember that 'frustratingly' describes doing something in a way that causes that disappointment.
No commonly confused words.