It is a hub.
Unicycle = 1 wheel. Bicycle = 2 wheels. Tricycle = 3 wheels.
I think you looking for a bicycle called the Penny-farthing, an early design of bicycle that had a very large front wheel.It is called a penny-farthing. Called that because the difference between the big wheel and the small wheel was similar to the difference between the old British pre-decimal penny and the farthing.
unicycle
The size of a bicycle wheel labeled "27x1 1/4" refers to a wheel with a diameter of 27 inches and a width of 1 1/4 inches.
bicycle: bi=2 cycle=circle/wheel. monocycle: mono=1 tricycle: tri=three If it doesn't have two wheels then by definition it cannot be called a bicycle .
bicycle with a basket
The gears on the rear wheel are called a cassette
The standard size of bicycle wheel bearings is typically 1/4 inch in diameter.
The term for lifting the front wheel of a bicycle off the ground while balancing on the rear wheel is called a "wheelie."
Tyre
If it has only one wheel it's a Unicycle .