IPA: /ɪnˈfjʊəreɪtɪŋli/
KK: /ɪnˈfjʊəreɪtɪŋli/
In a way that causes great anger or frustration.
The instructions were infuriatingly unclear, making the task much harder than it needed to be.
Infuriatingly → It is formed from "in-" (meaning not) and "furiare" (meaning to make furious) combined with the suffix "-ing" (indicating the action or process) and "-ly" (meaning in a manner). The word describes the manner in which something causes a state of extreme anger or frustration.
Think of something that makes you 'furious' ('furiare') and remember that 'infuriatingly' describes how that something causes anger.