suddenly and loudly; burst out
Describes a sudden, loud outburst of sound or emotion, such as crying, laughing, or shouting. Often used with verbs like 泣く, 笑う, or 叫ぶ.
The baby suddenly burst out crying loudly.
A loud burst of laughter erupted from the venue.
Mixed-kana spelling; less common but occasionally seen.
Onomatopoeic formation; the sound わっ suggests a sudden, forceful release of voice or emotion.