An onomatopoeic/mimetic adverb describing gentle, often repeated swaying, rocking, or wavering (physically or figuratively).
海の上で船がゆらゆら揺れている。
The boat is swaying gently on the sea.
木の枝が風でゆらゆらと揺れている。
The tree branches are swaying in the wind.
最近、気持ちがゆらゆらして決められない。
Lately my feelings have been wavering and I can't decide.