The Collaborative International Dictionary of English v.0.48:

Unpack \Un*pack"\, v. t. [1st pref. un- + pack.]
   [1913 Webster]
   1. To separate and remove, as things packed; to open and
      remove the contents of; as, to unpack a trunk.
      [1913 Webster]

   2. To relieve of a pack or burden. [R.] --Shak.
      [1913 Webster]

WordNet (r) 3.0 (2006):

unpack
    v 1: remove from its packing; "unpack the presents" [syn:
         unpack, take out] [ant: pack]

Moby Thesaurus II by Grady Ward, 1.0:

44 Moby Thesaurus words for "unpack":
   bare, break bulk, break the seal, bring to light, develop,
   disburden, discharge, disclose, discover, dismask, draw the veil,
   dump, expose, impart, lay bare, lay open, let daylight in, let out,
   manifest, off-load, open, open up, raise the curtain, reveal, show,
   show up, strip bare, unburden, uncloak, uncover, undrape, unfold,
   unfurl, unkennel, unlade, unload, unmask, unroll, unscreen,
   unsheathe, unship, unshroud, unveil, unwrap