IPA: /ɪˈrɛl.ə.vənt/
KK: /ɪˈrɛləvənt/
Not connected or related to the topic or situation being discussed.
The comments he made were completely irrelevant to the discussion.
Irrelevant → It is formed from "in-" (meaning not) and "relevare" (meaning to lift up or raise). The word "irrelevant" means not raised up or not pertinent to the matter at hand.
Think of something that is 'not' ('in-') 'lifted up' or 'raised' ('relevare') in importance — that's why it is considered irrelevant.