The Collaborative International Dictionary of English v.0.48:

Raiment \Rai"ment\ (r[=a]"ment), n. [Abbrev. fr. arraiment. See
   Array.]
   1. Clothing in general; vesture; garments; -- usually
      singular in form, with a collective sense.
      [1913 Webster]

            Living, both food and raiment she supplies.
                                                  --Dryden.
      [1913 Webster]

   2. An article of dress. [R. or Obs.] --Sir P. Sidney.
      [1913 Webster]

WordNet (r) 3.0 (2006):

raiment
    n 1: especially fine or decorative clothing [syn: array,
         raiment, regalia]
    v 1: provide with clothes or put clothes on; "Parents must feed
         and dress their child" [syn: dress, clothe, enclothe,
         garb, raiment, tog, garment, habilitate, fit
         out, apparel] [ant: discase, disrobe, peel,
         strip, strip down, uncase, unclothe, undress]

Moby Thesaurus II by Grady Ward, 1.0:

70 Moby Thesaurus words for "raiment":
   apparel, array, attire, bedeck, bedizenment, bedrape, bundle up,
   clad, clothe, clothes, clothing, costume, deck, dight, drape,
   drapery, dress, dressing, dud, duds, enclothe, endue, enrobe,
   enshroud, envelop, enwrap, fashion, fatigues, feathers, fig, frock,
   garb, garment, garments, gear, gown, guise, habiliment,
   habiliments, habilitate, habit, invest, investiture, investment,
   lap, linen, muffle up, rag, rag out, rags, robe, robes, sheathe,
   shroud, sportswear, style, swaddle, swathe, things, threads, tire,
   togs, toilette, trim, vestment, vesture, wear, wearing apparel,
   wrap, wrap up