The Collaborative International Dictionary of English v.0.48:

Subdivide \Sub`di*vide"\, v. t. [imp. & p. p. Subdivided; p.
   pr. & vb. n. Subdividing.] [L. subdividere, sub under +
   dividere to divide. See Divide.]
   To divide the parts of (anything) into more parts; to part
   into smaller divisions; to divide again, as what has already
   been divided.
   [1913 Webster]

         The progenies of Cham and Japhet swarmed into colonies,
         and those colonies were subdivided into many others.
                                                  --Dryden.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Subdivide \Sub`di*vide"\, v. i.
   To be, or to become, subdivided.
   [1913 Webster]

WordNet (r) 3.0 (2006):

subdivide
    v 1: form into subdivisions; "The cells subdivided"
    2: divide into smaller and smaller pieces; "This apartment
       cannot be subdivided any further!"

Moby Thesaurus II by Grady Ward, 1.0:

90 Moby Thesaurus words for "subdivide":
   alphabetize, analyze, anatomize, apportion, arrange, assay, assort,
   bifurcate, bisect, branch, break down, break up, by two, catalog,
   categorize, class, classify, cleave, codify, contradistinguish,
   cut in two, cut up, demarcate, demark, dichotomize, differentiate,
   digest, dimidiate, discriminate, dissect, distinguish, district,
   divide, divide up, divvy, divvy up, draw the line, file, fission,
   fork, grade, group, halve, in half, index, list,
   mark the interface, order, parcel, parcel out, partition, pick out,
   pigeonhole, place, portion, ramify, range, rank, rate, reduce,
   reduce to elements, resolve, screen, screen out, section, segment,
   segregate, select, separate, set a limit, set apart, set off,
   sever, severalize, sieve, sieve out, sift, sift out, sort,
   sort out, split, split hairs, split in two, split up, subtilize,
   tabulate, transect, type, winnow, zone