The Collaborative International Dictionary of English v.0.48:

Group \Group\, v. t. [imp. & p. p. Grouped; p. pr. & vb. n.
   Grouping.] [Cf. F. grouper. See Group, n.]
   To form a group of; to arrange or combine in a group or in
   groups, often with reference to mutual relation and the best
   effect; to form an assemblage of.
   [1913 Webster]

         The difficulty lies in drawing and disposing, or, as
         the painters term it, in grouping such a multitude of
         different objects.                       --Prior.
   [1913 Webster]

   Grouped columns (Arch.), three or more columns placed upon
      the same pedestal.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Grouping \Group"ing\ (gr[=oo]p"[i^]ng), n. (Fine Arts)
   The disposal or relative arrangement of figures or objects,
   as in, drawing, painting, and sculpture, or in ornamental
   design.
   [1913 Webster]

WordNet (r) 3.0 (2006):

grouping
    n 1: any number of entities (members) considered as a unit [syn:
         group, grouping]
    2: the activity of putting things together in groups
    3: a system for classifying things into groups [syn: grouping,
       pigeonholing]

Moby Thesaurus II by Grady Ward, 1.0:

182 Moby Thesaurus words for "grouping":
   Bund, Rochdale cooperative, age group, alliance, analysis,
   appraisal, arrangement, assemblage, assessment, association,
   assortment, atmosphere, axis, balance, band, batch, battalion,
   bevy, bloc, blood, body, bracket, branch, brigade, brushwork,
   bunch, cabal, cast, caste, cataloging, categorization, category,
   clan, class, classification, clique, clump, cluster, coalition,
   codification, cohort, college, color, combination, combine,
   common market, company, complement, composition, confederacy,
   confederation, consumer cooperative, contingent, cooperative,
   cooperative society, copse, corps, coterie, council, covey,
   credit union, crew, crop, crowd, culling, customs union, design,
   detachment, detail, division, draftsmanship, economic community,
   estate, evaluation, faction, factoring, federation, filing, fleet,
   free trade area, gang, gauging, gradation, grade, grading, group,
   groupment, grove, hassock, head, heading, identification, in-group,
   indexing, junta, kin, knot, label, league, level, line, lot,
   machine, mess, mob, movement, order, out-group, outfit, pack,
   painterliness, partnership, party, peer group, perspective,
   phalanx, pigeonhole, pigeonholing, placement, platoon,
   political machine, position, posse, predicament, race, ranging,
   rank, ranking, rating, regiment, ring, rubric, salon, screening,
   section, selection, sept, set, shading, shadow, shock, sifting,
   sifting out, slew, society, sorting, sorting out, squad, stable,
   station, status, stook, strain, stratification, stratum, string,
   subdivision, subgroup, suborder, subordination, tabulation,
   taxonomy, team, technique, thicket, tier, title, tone, treatment,
   triage, tribe, troop, troupe, tuft, tussock, typology, union,
   values, weighing, wing, winnowing, wisp