IPA: /ɪˈrɛvərəntli/
KK: /ɪˈrɛvərəntli/
In a way that shows a lack of respect for people or things that are generally taken seriously.
He spoke irreverently about the traditions that everyone else held dear.
Irreverently → It is formed from "in-" (meaning not) and "reverent" (from Latin "reverentem", meaning to stand in awe or respect) and the suffix "-ly" (meaning in a manner of). The word "irreverently" means in a manner that shows a lack of respect or awe.
Think of 'not' ('in-') showing 'awe' ('reverent') — that's why behaving irreverently means acting without respect.