Depends on what you mean. If you're skilled enough you can get on backwards on just about any bike, and ride it facing the wrong way.
If you've got what's called a fixie(a bike where the pedals always move then the rear wheel moves) then it can be ridden backwards.
If you've got a bike with a freecoaster rear hub you can roll backwards down a ramp or something like that.
Fixie bike are bikes (usually road bike frames) that have a fixed rear sprocket which allows you to pedal forward like normal, but does not allow you to just coast . If you pedal backwards it goes backwards if you pedal slow it will remain slow. The whole point of a fixie is to eliminate brakes shifters to simplify a road bike.
the 49ers
When you try to ride a bike with the pedals moving only backwards and not forward, the bike will not move forward. The pedals need to move in a forward motion in order for the bike to propel forward.
the equation of 5678r764
Time.
the moon goes backwards
Of course.
F.E.A.R by Ian Brown
you need a special wheel that has a "coaster brake"
My bike goes inside of my garage.
A cat going backwards says woem, woem (meow backwards).
No because the bike would brake evry time so no