The Collaborative International Dictionary of English v.0.48:

Container \Con*tain"er\, n.
   1. One who, or that which, contains; particularly, an
      artifactual object that is designed to contain some fluid
      or solid material, object or objects, especially for
      convenience in transporting the contained objects.
      [1913 Webster]

   2. a large metallic box designed to hold many smaller boxes
      or packages, and used for convenience in loading and
      unloading large quantities of freight, such as on ships,
      trains, or airplanes.
      [PJC]

WordNet (r) 3.0 (2006):

container
    n 1: any object that can be used to hold things (especially a
         large metal boxlike object of standardized dimensions that
         can be loaded from one form of transport to another)

Moby Thesaurus II by Grady Ward, 1.0:

25 Moby Thesaurus words for "container":
   arena, cincture, close, confine, coop, court, courtyard, curtilage,
   delimited field, enclave, enclosure, field, fold, ground, list,
   pale, paling, park, pen, quad, quadrangle, square, theater, toft,
   yard