IPA: /spɛkˈtækjʊlərli/
KK: /spɛkˈtækjʊlərli/
In a way that is very impressive or exciting; remarkably.
The fireworks display was spectacularly beautiful, lighting up the night sky.
Spectacularly → It is formed from "spectacular" (from Latin "spectaculum", meaning a show or sight) and the suffix "-ly" (meaning in a manner of). The word "spectacularly" means in a manner that is impressive or striking to see, as if it were a show.
Think of something that is a 'show' or 'sight' ('spectaculum') and remember that doing it 'in a manner' ('-ly') makes it spectacular.