The Collaborative International Dictionary of English v.0.48:

Pigeonhole \Pi"geon*hole`\, v. t.
   To place in the pigeonhole of a case or cabinet; hence, to
   put away; to lay aside indefinitely; as, to pigeonhole a
   letter or a report.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Pigeonhole \Pi"geon*hole`\, n.
   A small compartment in a desk or case for the keeping of
   letters, documents, etc.; -- so called from the resemblance
   of a row of them to the compartments in a dovecote. --Burke.
   [1913 Webster]

WordNet (r) 3.0 (2006):

pigeonhole
    n 1: a specific (often simplistic) category
    2: a small compartment [syn: cubbyhole, pigeonhole]
    v 1: place into a small compartment
    2: treat or classify according to a mental stereotype; "I was
       stereotyped as a lazy Southern European" [syn: pigeonhole,
       stereotype, stamp]

Moby Thesaurus II by Grady Ward, 1.0:

188 Moby Thesaurus words for "pigeonhole":
   adjourn, air hole, alphabetize, analyze, armhole, arrange, assort,
   bibliography, blood, blowhole, book, bracket, branch, break down,
   bullet-hole, bunghole, calendar, card catalog, caste, catalog,
   catalogue raisonne, categorize, category, clan, class,
   classified catalog, classify, codify, constitute, continue,
   cringle, cubby, cubbyhole, deadeye, decree, defer, delay, digest,
   divide, division, doghouse, drag out, enact, enact laws, enroll,
   enter, enumerate, estate, extend, eye, eyelet, file, filibuster,
   filing system, finding list, gasket, get the floor, grade, grommet,
   group, grouping, guide, handlist, hang fire, hang up,
   have the floor, head, heading, hold off, hold over, hold up, hole,
   identify, impanel, index, inventory, itemize, keep score, keyhole,
   kill, kin, knothole, label, lay aside, lay away, lay by, lay over,
   league, legislate, letter file, level, list, lobby through,
   logroll, loop, loophole, manhole, mousehole, name, niche, ordain,
   order, pass, peephole, pigeonholes, pinch, pinhole, place, placket,
   placket hole, playhouse, pocket, porthole, position, post,
   postpone, predicament, program, prolong, prorogate, prorogue,
   protract, punch-hole, push aside, put aside, put away,
   put in force, put in mothballs, put off, put on ice, put through,
   race, railroad through, range, rank, rate, rating, recess,
   register, reserve, roll logs, rubric, schedule, score, section,
   sept, set, set aside, set by, shelve, shift off, sideline,
   sleep on, slot, sort, spiracle, stand over, station, status,
   stave off, stay, store, stow, strain, stratum, stretch out,
   subdivide, subdivision, subgroup, suborder, suspend, table,
   table the motion, tabulate, take a recess, take the floor, tally,
   tap, tier, tight spot, tight squeeze, title, type, vent, venthole,
   veto, waive, yield the floor