wheeler

1. One that wheels.
2. A thing that moves on or is equipped with wheels or a wheel. Often used in combination: a three-wheeler; a paddle-wheeler.
3. A wheel horse.

1. Winder in a stair, especially a newel or spiral stair.

2. Lower part of a battlement. Wheelers (embrasures) and kneelers (merlons or cops) therefore refer to crenellation.

The noun has 4 meanings:

Meaning #1: someone who makes and repairs wooden wheels
  Synonym: wheelwright

Meaning #2: the man at the outermost end of the rank in wheeling

Meaning #3: a person who rides a bicycle
  Synonyms: cyclist, bicyclist, bicycler

Meaning #4: a draft horse harnessed behind others and nearest the wheels of a vehicle
  Synonym: wheel horse