a solid bounded by a cylindrical surface and two parallel planes (the bases)
"The engineer sketched a cylinder to represent the piston inside the engine block."
a surface generated by rotating a parallel line around a fixed line
"The mathematical definition of a cylinder describes it as a surface created when a straight line moves parallel to itself while revolving around a central axis."
a chamber within which piston moves
"The engine's cylinder compresses the air-fuel mixture before ignition."
a cylindrical container for oxygen or compressed air
"The firefighter quickly attached the hose to the green cylinder containing fresh oxygen."
A surface created by projecting a closed two-dimensional curve along an axis intersecting the plane of the curve.
"The geometric cylinder is formed by projecting a circle along an axis perpendicular to its plane."
In plain English: A cylinder is a three-dimensional shape that has two flat circular ends and a curved side connecting them, looking like a can or pipe.
"The new car has a six-cylinder engine that runs smoothly on all roads."
Usage: The most common everyday meaning refers to a solid object with circular ends and straight sides, such as a gas cylinder or pencil lead container. Avoid confusing this physical shape with the verb form, which means to smooth paper by pressing it between rollers.
To calender; to press (paper, etc.) between rollers to make it glossy.
"The heavy cylinder was used to calender the raw paper sheets until their surface became perfectly smooth and glossy."
In plain English: To cylinder something means to shape it into a round, tube-like form with flat ends.
"The printer cylinder jammed again after I loaded too many sheets at once."
The word cylinder comes from the Latin cylindrus, which was borrowed from Ancient Greek for a rolling pin or something that rolls. It ultimately derives from a Greek verb meaning "to roll" or "to wallow."