To be noisy or astir; to rustle or murmur—people or places becoming lively with murmurs and noises (usually written in kana).
会場が発表と同時にざわめいた。
The venue murmured as soon as the announcement was made.
新聞で大きな記事が出ると町中がざわめいた。
When a big news story appeared in the paper, the whole town was abuzz.
森の中で何かが動き、木立がざわめいた。
Something moved in the forest and the trees rustled.