What is "chorda filum"

Sea laces \Sea" la"ces\ (Bot.) A kind of seaweed ( Chorda Filum) having blackish cordlike fronds, often many feet long.

Chorda filum, commonly known as dead man's rope or sea lace among other names, is a species of brown algae in the genus Chorda. It is widespread in the temperate waters of the northern hemisphere. The species also has numerous other common names related to its physical appearance. Names include mermaid's tresses, cat's gut, bootlace weed, seatwine, and mermaid's fishing line.