IPA: /ˌɒstənˈteɪʃəsli/
KK: /ɔːˈstɛntəˌteɪʃəsli/
In a way that is meant to attract attention or impress others, often by being overly showy or extravagant.
She dressed ostentatiously for the party, wearing a sparkling gown and flashy jewelry.
Ostentatiously → It is formed from "ostentare" (meaning to display) and the suffix "-iously" (meaning in a manner characterized by). The word describes an action done in a manner that is characterized by a display or showiness.
Think of someone displaying something in a very noticeable way — 'ostentare' means to display, and '-iously' means in a manner that shows.