Merriam-Webster Collegiate Dictionary - driver

 noun  Date: 14th century one that drives: as  a. coachman  b. the operator of a motor vehicle  c. an implement (as a hammer) for driving  d. a mechanical piece for imparting motion to another piece  e. one that provides impulse or motivation a ~ in this economy  f. a golf wood with a nearly straight face used in driving  g. an electronic circuit that supplies input to another electronic circuit; also loudspeaker  h. a piece of computer software that controls input and output operations  • ~less adjective