IPA: /ˈθʌndərəsli/
KK: /ˈθʌndərəsli/
In a way that is very loud and powerful, like thunder.
The crowd cheered thunderously after the team's victory.
Thunderously → It is formed from "thunder" (from Old English *þunor*, meaning a loud noise or rumble) and the suffix "-ously" (meaning in a manner characterized by). The word "thunderously" means in a manner characterized by loud noise or rumbling, similar to thunder.
Think of the loud noise of thunder and remember that when something happens 'thunderously', it is happening in a loud and rumbling manner.