Spider definition1. On a bicycle , the multiarmed piece to which the chainwheels are bolted, usually welded to or part of the right crankarm .
2. A four arm piece on a constant velocity joint
3. A type of sport vehicle. In the early 1900s it meant a light two-seater car. In the 1950s the word was revived by some Italian manufacturers for an open two seater sports car . Also spelled "spyder." See Alfa Romeo