Meaning of SPROCKET in English

SPROCKET

[sprock.et] n [origin unknown] (1750) 1: a toothed wheel whose teeth engage the links of a chain

2: a cylinder with teeth around the circumference at either end that project through perforations in something (as motion-picture film) to move it through a mechanism (as a projector)

Merriam-Webster English vocab.      Английский словарь Merriam Webster.