Definitions of sober:

• verb:   cause to become sober

  Example: "A sobering thought"

• verb:   become sober after excessive alcohol consumption

  Example: "Keep him in bed until he sobers up"

• verb:   become more realistic

  Example: "After thinking about the potential consequences of his plan, he sobered up"

• adjective:   not affected by a chemical substance (especially alcohol)
• adjective:   lacking brightness or color; dull

  Example: "Sober Puritan gray"

• adjective:   dignified and somber in manner or character and committed to keeping promises

  Example: "As sober as a judge"

• adjective:   completely lacking in playfulness
• name:  A surname (very rare: popularity rank in the U.S.: #19419)