Pomposity is the way someone talks or acts when they want everyone to see them as important. They sound stiff and formal, and they use long words, as if they are giving a speech even in a small room. We use this word when we do not like that behaviour. It is a noun: it names the quality, or a remark full of that quality, not the person. Though actually the older idea behind it is pomp — a grand public show, like a parade. The insult came later, when all that grandeur started to feel fake.