IPA: //ˈpɒmpəsli//
KK: /ˈpɑmpəsli/
In a way that shows excessive pride or self-importance, often in a way that is annoying to others.
He spoke pompously about his achievements, making everyone else feel uncomfortable.
Pompously → It is formed from "pomp" (from Latin *pompa*, meaning a procession or display) and the suffix "-ously" (meaning in a manner characterized by). The word "pompously" means in a manner characterized by grandeur or ostentation, often implying arrogance.
Think of a grand 'procession' ('pomp') that is done 'in a manner' ('-ously') that shows off — that's why pompously means showing off in a grand way.