1. [n]  persons who administer the law
2. [n]  someone who manages a government agency or department
3. [n]  a person responsible for the administration of a business
4. [adj]  having the function of carrying out plans or orders etc.; "the executive branch"

1. \Ex*ec"u*tive\, a. [Cf.F. ex['e]cutif.]
   Designed or fitted for execution, or carrying into effect;
   as, executive talent; qualifying for, concerned with, or
   pertaining to, the execution of the laws or the conduct of
   affairs; as, executive power or authority; executive duties,
   officer, department, etc.
   Note: In government, executive is distinguished from
         legislative and judicial; legislative being applied to
         the organ or organs of government which make the laws;
         judicial, to that which interprets and applies the
         laws; executive, to that which carries them into effect
         or secures their due performance.
   

2. \Ex*ec"u*tive\, n.
   An impersonal title of the chief magistrate or officer who
   administers the government, whether king, president, or
   governor; the governing person or body.
   

The command interpreter or shell for an operating system. The term is used especially around mainframes and probably derived from UNIVAC's archaic EXEC 2 and current (in 2000) EXEC 8 operating systems.