1. (Science: zoology) 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.
spiders are divided into two principal groups: the dipneumona, having two lungs: and the Tetrapneumona, having four lungs. See mygale. The former group includes several tribes; as, the jumping spiders (see saltigradae), the wolf spiders, or Citigradae (see under Wolf), the crab spiders, or Laterigradae (see under Crab), the garden, or geometric, spiders, or Orbitellae (see under geometrical, and Garden), and others. See bird spider, grass spider, house spider, silk spider.
5. (Science: machinery) 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. Spider ant.
Origin: OE. Spire, fr. AS. Spinnan to spin; so named from spinning its web; cf. D. Spin a spider, G. Spinne, Sw. Spindel. Seee Spin.