Which word means presumptuously arrogant?

Overweening is the word that means presumptuously arrogant. This term conveys a sense of excessive pride or confidence that often disregards the opinions or feelings of others. When someone is described as overweening, it emphasizes not just arrogance, but an overstepping of boundaries, suggesting that they hold themselves in higher regard than is justified. It captures a specific quality of arrogance that is presumptuous, indicating an unwarranted assumption of superiority.

In contrast, ostentatious refers to a showy display intended to attract attention or impress others, which does not inherently include arrogance. Pompous describes someone who is self-important and overly formal in manner, but it lacks the nuance of presumption. Vainglorious also pertains to excessive pride, particularly in one's achievements or qualities, but it does not as directly imply the presumptuousness that overweening does. Therefore, overweening is the most precise choice for denoting presumptuous arrogance.