IPA: /ˈbɔɪstərəsli/
KK: /ˈbɔɪstərəsli/
In a way that is noisy, energetic, and cheerful.
The children played boisterously in the park, laughing and shouting.
Boisterously → It is formed from "boisterous" (from Middle English *boistous*, meaning rough or noisy) and the suffix "-ly" (meaning in a manner of). The word "boisterously" means in a rough or noisy manner.
Think of someone being rough or noisy ('boisterous') and how the '-ly' makes it describe the manner of that behavior.