What is the meaning of Arachnoid?

Relating to or resembling spider webs; covered with or composed of soft loose hairs or fibers.

Relating to the arachnoid mater.

Ellipsis of arachnoid mater..

A round network of fractures in the crust of Venus.

Relating to or resembling spiders.

An arachnid.

Source: wiktionary.org