(1) An arthropod of the order Araneida (subclass Arachnida) characterized by four pairs of legs; a cephalothorax; a globose, smooth abdomen; and a complex of web-spinning spinnerets. Among the venomous spiders found in the New World are the black widow spider, Latrodectus mactans; red-legged widow spider, Latrodectus bishopi; pruning spider, or Peruvian tarantula, Glyptocranium gasteracanthoides; Chilean brown spider, Loxosceles laeta; Peruvian brown spider, Loxosceles rufipes; brown recluse spider of North America, Loxosceles reclusus. (2) An obstructive growth in the teat of a cow. [O. E. spinnan, to spin]