sprocket

noun4

1. •
   A toothed wheel that enmeshes with a chain or other perforated band.
2. •
   A placeholder name for an unnamed, unspecified, or hypothetical manufactured good or product.

   • Suppose we have a widget factory that produces 100 widgets per year, and a sprocket factory that produces 200 sprockets per year.
3. •
   [usually plural] The tooth of such a wheel.
4. •
   A flared extension at the base of a sloped roof.