What is Non-executive Director?

Legal Definition
A non-executive director (abbreviated to non-exec, NED or NXD) or external director is a member of the board of directors of a company or organisation who does not form part of the executive management team. They are not employees of the company or affiliated with it in any other way and are differentiated from inside directors, who are members of the board who also serve or previously served as executive managers of the company (most often as corporate officers). However they do have the same legal duties, responsibilities and potential liabilities as their executive counterparts.

Non-executive directors are directors who act in advisory capacity only. Typically, they attend monthly board meetings to offer the benefit of their advice and serve on committees concerned with sensitive issues such as the pay of the executive directors and other senior managers; they are usually paid a fee for their services but are not regarded as employees.

All directors should be capable of seeing company and business issues in a broad perspective. Nonetheless, non-executive directors are usually chosen because of their independence and initiatives, and are of an appropriate caliber and have particular personal qualities.
-- Wikipedia
Legal Definition
An independant director who is not a member of the management team.