noun, noun or participle which takes 'suru'
Archaic noun or suru-verb describing a shaking or swaying motion. Not used in modern everyday Japanese; found mainly in classical literature or poetic language.
古い和歌に「舟の揺蕩」という表現が見られる。
In old waka poetry, one can find the expression 'the swaying of the boat'.
The exact derivation is uncertain; the kanji 揺 (shake) and 蕩 (melt, sway) combine to suggest a wavering motion. The reading ようとう is a Sino-Japanese on'yomi compound.