The cylindrical part of a hinge is called a knuckle.
In some areas it is also called the barrel.
A knuckle.
hinge
Hinge joints include a cylindrical bone end that fits into a groove, called a trochlea, on the other bone. One example is your elbow.
door hinge pin
The oldest part of a clams shell is the outside part of the hinge. This is because the clam starts at the hinge and grows outwards.
Cylindrical.
Hinge joints are joints that connect on part of an adjoining part of the body. Pain relief in for hinge joint pain consists of pain relievers, braces, and in some cases surgery.
It got its name because it acts as a hinge, only opening and closing a certain distance. Your elbow is a hinge joint. Think of your elbow as a hinge on a door in your house. The door is your forearm and the door frame is your upper arm/body.
rouleau
The theorem emulates the action of a hinge. As the angle of the hinge is increased the distance between the free edges increases.
Don't know what a "bushy" is but maybe you're thinking about a bushing. A bushing on a car is usually a cylindrical "sleeve" that's used if you want to attach one part to another but still allowing them to move a little. Think of it as a hinge lined with rubber. A regular hinge would seize and jam unless the halves are perfectly aligned, but with a rubber sleeve in one half, the parts have some degree of freedom to move.
Synovial pivotal hinge