1. [n]  an alphabetical list of names and addresses
2. [n]  (computer science) a listing of the files stored in memory (usually on a hard disk)

1. \Di*rect"o*ry\, a. [L. directorius.]
   Containing directions; enjoining; instructing; directorial.
   

2. \Di*rect"o*ry\, n.; pl. {Directories}.
   1. A collection or body of directions, rules, or ordinances;
      esp., a book of directions for the conduct of worship; as,
      the Directory used by the nonconformists instead of the
      Prayer Book.
   2. A book containing the names and residences of the
      inhabitants of any place, or of classes of them; an
      address book; as, a business directory.
   3. [Cf. F. directoire.] A body of directors; board of
      management; especially, a committee which held executive
      power in France under the first republic.
   4. Direction; guide. [R.] --Whitlock.
   

A node in a hierarchical file system which contains zero or more other nodes - generally, files or other directories.

Compare folder.