IPA: /ɪˈrɛlɪvəntli/
KK: /ɪˈrɛlɪvəntli/
In a way that is not related to the subject or situation being discussed.
He kept talking about his vacation irrelevantly during the meeting.
Irrelevantly → It is formed from "in-" (meaning not), "relevant" (from Latin "relevare", meaning to lift up or raise), and "-ly" (meaning in a manner). The word "irrelevantly" means in a manner that is not related or pertinent to the matter at hand.
Think of 'not' ('in-') and 'lifting up' ('relevare') to remember that 'irrelevantly' means something that is not related or pertinent.