What is "beche de mer"

Holothurian \Hol`o*thu"ri*an\, a. (Zo["o]l.) Belonging to the Holothurioidea. -- n. One of the Holothurioidea.

Note: Some of the species of Holothurians are called sea cucumbers, sea slugs, trepang, and b[^e]che de m[`e]r. Many are used as food, esp. by the Chinese. See Trepang.

Trepang \Tre*pang"\, n. [Malay tr[=i]pang.] (Zo["o]l.) Any one of several species of large holothurians, some of which are dried and extensively used as food in China; -- called also b[^e]che de mer, sea cucumber, and sea slug. [Written also tripang.]

Note: The edible trepangs are mostly large species of Holothuria, especially Holothuria edulis. They are taken in vast quantities in the East Indies, where they are dried and smoked, and then shipped to China. They are used as an ingredient in certain kinds of soup.