|n.||1.||(Zool.) Any one of numerous species of arachnids comprising the order Araneina. Spiders have the mandibles converted into poison fangs, or falcers. The abdomen is large and not segmented, with two or three pairs of spinnerets near the end, by means of which they spin threads of silk to form cocoons, or nests, to protect their eggs and young. Many species spin also complex webs to entrap the insects upon which they prey. The eyes are usually eight in number (rarely six), and are situated on the back of the cephalothorax. See Illust. under Araneina.|
|2.||(Zool.) Any one of various other arachnids resembling the true spiders, especially certain mites, as the red spider (see under Red).|
|3.||An iron pan with a long handle, used as a kitchen utensil in frying food. Originally, it had long legs, and was used over coals on the hearth.|
|4.||A trevet to support pans or pots over a fire.|
|5.||(Mach.) A skeleton, or frame, having radiating arms or members, often connected by crosspieces; as, a casting forming the hub and spokes to which the rim of a fly wheel or large gear is bolted; the body of a piston head; a frame for strengthening a core or mold for a casting, etc.|
|Noun||1.||spider - predatory arachnid that usually has silk-spinning organs at the back end of the body; they spin silk to make cocoons for eggs or traps for prey|
|2.||spider - a computer program that prowls the internet looking for publicly accessible resources that can be added to a database; the database can then be searched with a search engine|
|3.||spider - a skillet made of cast iron|
|(World-Wide Web)||spider - (Or "robot", "crawler") A program that
automatically explores the World-Wide Web by retrieving a
document and recursively retrieving some or all the documents
that are referenced in it. This is in contrast with a normal
web browser operated by a human that doesn't automatically
follow links other than inline images and URL redirection.|
The algorithm used to pick which references to follow strongly depends on the program's purpose. Index-building spiders usually retrieve a significant proportion of the references. The other extreme is spiders that try to validate the references in a set of documents; these usually do not retrieve any of the links apart from redirections.
The standard for robot exclusion is designed to avoid some problems with spiders.
Early examples were Lycos and WebCrawler.