Solid bounded by a curved surface and by two plane surfaces.
The two plane surfaces are parallel and congruent.
Solid bounded by a cylindrical surface whose directrix is a closed curve and by two parallel planes that do not have any generatrices.
Example
A cylinder is formed by two parallel and congruent planes called its bases and a curved surface called its lateral surface.
Many everyday objects have the shape of a cylinder: tin cans, soft drink cans, paint rollers, rolling pins, oil barrels, etc.,