1) Bicycle part 2) Mechanical power control 3) Motion-picture machine part 4) Pulley with teeth 5) Roller 6) Tooth on the rim of a wheel 7) Toothed metal wheel 1) Cog 
A sprocket or sprocket-wheel is a profiled wheel with teeth, cogs, or even sprockets that mesh with a chain, track or other perforated or indented material. The name `sprocket` applies generally to any wheel upon which are radial projections that engage a chain passing over it. It is distinguished from a gear in that sprockets are never meshed t.....
• (n.) A tooth or projection, as on the periphery of a wheel, shaped so as to engage with a chain. • (n.) A sprocket wheel.
(from the article `bicycle`) The rear derailleur moves the chain from one rear sprocket to the next. The front derailleur moves the chain from one front chainwheel to the next. ... Chain drives are widely used for the transmission of power where shafts are separated at distances greater than that for which gears are practical. ... [2...
The parts of the motorcycle that deliver and receive the power to the rear wheel, creating the final drive. The front sprocket runs off the transmission shaft. The rear sprocket is bolted to the hub of the rear wheel. They are connected together by a chain.
Sprock'et noun [ Etymology uncertain.] (Machinery) (a) A tooth or projection, as on the periphery of a wheel, shaped so as to engage with a chain. (b) A sprocket wheel. 
A toothed driving wheel used to move film through various machines by engaging with the perforated holes in film stock.
a circular plate with teeth machined around outside to engage links of a chain.
A sprocket or sprocket wheel is a toothed wheel engaging with a conveyor or power chain, such as occurs on the backwheel a typical bicycle or motorbike.
[n] - roller that has teeth on the rims to pull film or paper through 2. [n] - thin wheel with teeth that engage with a chain
sprocket wheel noun thin wheel with teeth that engage with a chain
The teeth on a roller designed to engage with the perforations in film. Sometimes sprocket holes are referred to as sprockets too
See cog.