IPA: /ˈɪrɪteɪɪŋli/
KK: /ɪrɪˈteɪɪŋli/
In a way that causes annoyance or discomfort.
She spoke irritatingly, making it hard for anyone to concentrate.
Irritatingly → It is formed from "irritate" (from Latin "irritare", meaning to provoke or annoy) and the suffix "-ly" (meaning in a manner of). The word "irritatingly" describes the manner in which something provokes annoyance or discomfort.
Think of something that provokes annoyance ('irritate') and remember that 'irritatingly' means doing so in a way that is bothersome.