IPA: /əbˈnɒkʃəsli/
KK: /əbˈnɑkʃəsli/
In a way that is very unpleasant or offensive to others.
He spoke obnoxiously during the meeting, making everyone uncomfortable.
Obnoxiously → It is formed from "ob-" (meaning against) and "noxius" (from Latin, meaning harmful or hurtful) combined with the suffix "-ly" (meaning in a manner of). The word "obnoxiously" means in a manner that is harmful or offensive, often to an extreme degree.
Think of being 'against' ('ob-') something that is 'harmful' ('noxius') — that's why behaving obnoxiously means acting in a way that is very offensive.