Learn English – difference between “loosen” and “unscrew” for lid/cap

Strictly speaking, cyclist includes someone riding a cycle with a number of wheels other than two: unicycle, tricycle or quadricycle.

However, the use of bicyclist nowadays is not very common. Unless of course there was a mixed group of bicyclists and tricyclists and you wanted to be specific.

When a verb has no object, we call it intransitive:

Shoes wear out.

When a verb takes an object, we call it transitive:

Running on concrete wore out his knees.

"His knees" is the object. "Running on concrete" is the subject.

We can "flip" a transitive verb in the active voice (see the sentence about "knees" above) and make it a passive construction:

His knees were worn out by running on concrete.

We can omit the agent (that which performs the action):

His knees were worn out.

Something wore his knees out, but we don't know what it was. Was he a fireman who climbed ladders all day? In this form, we're basically saying his knees are in certain state or condition, since the agent is unexpressed.