Meaning of backseat driver

back'seat driv'er

Pronunciation: [key]
  1. an automobile passenger who offers the driver unsolicited advice, warnings, criticism, etc., esp. from the backseat.
  2. any person who, by means of criticism, unsolicited advice, or the like, interferes in affairs that are not his or her concern or responsibility.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.