IPA: //ɡrænˈdɪləkwəntli//
KK: /grænˈdɪləkwəntli/
In a way that is extravagant or pompous in speech or writing, often using elaborate language.
The speaker grandiloquently described his achievements, impressing the audience with his elaborate vocabulary.
Grandiloquently → It is formed from "grandis" (meaning large or grand) and "loqui" (meaning to speak) combined with the adverbial suffix "-ly". The word describes a manner of speaking that is grand or lofty, often in a pompous way.
Think of someone speaking in a 'grand' manner ('grandis') — that's why grandiloquently means to speak in a grand or pompous way.