The Collaborative International Dictionary of English v.0.48:

Enrich \En*rich"\, v. t. [imp. & p. p. Enriched; p. pr. & vb.
   n. Enriching.] [F. enrichir; pref. en- (L. in) + riche
   rich. See Rich.]
   1. To make rich with any kind of wealth; to render opulent;
      to increase the possessions of; as, to enrich the
      understanding with knowledge.
      [1913 Webster]

            Seeing, Lord, your great mercy
            Us hath enriched so openly.           --Chaucer's
                                                  Dream.
      [1913 Webster]

   2. To supply with ornament; to adorn; as, to enrich a ceiling
      by frescoes.
      [1913 Webster]

   3. To make rich with manure; to fertilize; -- said of the
      soil; as, to enrich land by irrigation.
      [1913 Webster]

   4. To supply with knowledge; to instruct; to store; -- said
      of the mind. --Sir W. Raleigh.
      [1913 Webster]

WordNet (r) 3.0 (2006):

enrich
    v 1: make better or improve in quality; "The experience enriched
         her understanding"; "enriched foods" [ant: deprive,
         impoverish]
    2: make wealthy or richer; "the oil boom enriched a lot of local
       people" [ant: impoverish]

Moby Thesaurus II by Grady Ward, 1.0:

107 Moby Thesaurus words for "enrich":
   acculturate, add to, adorn, advance, ameliorate, amend, array,
   beautify, bedeck, bedizen, better, blazon, boost, bring forward,
   civilize, color, convolute, dandify, deck, deck out, decorate,
   dizen, doll up, dress, dress up, edify, educate, elaborate,
   elevate, embellish, emblazon, embroider, emend, endow, enhance,
   enlighten, fatten, favor, fecundify, fertilize, festoon, fig out,
   fix up, flourish, fortify, forward, foster, fructify, furbish,
   garnish, gild, go straight, grace, gussy up, impregnate, improve,
   improve upon, inseminate, involve, lard, lift, load with ornament,
   make an improvement, manure, meliorate, mend, nurture, ornament,
   overcharge, overlay, overload, paint, prank, prank up, preen,
   prettify, primp, primp up, prink, prink up, prolificate, promote,
   raise, redecorate, redo, refine, refine upon, reform, refurbish,
   restore, richen, set off, set out, smarten, smarten up, socialize,
   spruce up, straighten out, titivate, transfigure, transform,
   trick out, trick up, trim, upgrade, uplift, varnish