The Collaborative International Dictionary of English v.0.48:

Asunder \A*sun"der\, adv. [Pref. a- + sunder.]
   Apart; separate from each other; into parts; in two;
   separately; into or in different pieces or places.
   [1913 Webster]

         I took my staff, even Beauty, and cut it asunder.
                                                  --Zech. xi.
                                                  10.
   [1913 Webster]

         As wide asunder as pole and pole.        --Froude.
   [1913 Webster]

WordNet (r) 3.0 (2006):

asunder
    adv 1: into parts or pieces; "he took his father's watch apart";
           "split apart"; "torn asunder" [syn: apart, asunder]
    adj 1: widely separated especially in space; "as wide asunder as
           pole from pole"

Moby Thesaurus II by Grady Ward, 1.0:

49 Moby Thesaurus words for "asunder":
   adrift, all to pieces, apart, apart from, aside from,
   at a distance, away, away from, bipartite, by two, dichotomous,
   discontinuous, discrete, distal, distant, distinct, divergent,
   exotic, far, far off, faraway, fifty-fifty, half-and-half, in half,
   in halves, in the abstract, in twain, in two, incoherent, insular,
   long-distance, long-range, noncohesive, one by one, partitioned,
   piecemeal, remote, removed, separate, separated, separately,
   severally, sky-high, to shreds, unassociated, unattached,
   unattended, unconnected, unjoined