noun
sea cucumber
Refers to the marine animal; sometimes translated as 'sea slug' in anglicized haiku, but biologically distinct from nudibranchs (sea slugs).
See also: 海牛 (うみうし)
ナマコは海底でゆっくり動く。
Sea cucumbers move slowly along the ocean floor.
この地域ではナマコを酢の物にして食べる。
In this region, they eat sea cucumber as a vinegared dish.
Kanji form is rare and literary; the reading なまこ is a jukujikun.
海牛 (うみうし) refers to sea slugs (nudibranchs), which are gastropods, while ナマコ are echinoderms. They are often confused in translation.
The kanji 海鼠 literally means 'sea mouse', likely from the animal's shape. The reading なまこ is a jukujikun, and its origin is uncertain.