The Collaborative International Dictionary of English v.0.48:

Engross \En*gross"\, v. t. [imp. & p. p. Engrossed; p. pr. &
   vb. n. Engrossing.] [F., fr. pref. en- (L. in) + gros
   gross, grosse, n., an engrossed document: cf. OF. engrossir,
   engroissier, to make thick, large, or gross. See Gross.]
   1. To make gross, thick, or large; to thicken; to increase in
      bulk or quantity. [Obs.]
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            Waves . . . engrossed with mud.       --Spenser.
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            Not sleeping, to engross his idle body. --Shak.
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   2. To amass. [Obs.]
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            To engross up glorious deeds on my behalf. --Shak.
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   3. To copy or write in a large hand (en gross, i. e., in
      large); to write a fair copy of in distinct and legible
      characters; as, to engross a deed or like instrument on
      parchment.
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            Some period long past, when clerks engrossed their
            stiff and formal chirography on more substantial
            materials.                            --Hawthorne.
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            Laws that may be engrossed on a finger nail. --De
                                                  Quincey.
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   4. To seize in the gross; to take the whole of; to occupy the
      attention completely; to absorb; as, the subject engrossed
      all his thoughts.
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   5. To purchase either the whole or large quantities of, for
      the purpose of enhancing the price and making a profit;
      hence, to take or assume in undue quantity, proportion, or
      degree; as, to engross commodities in market; to engross
      power.
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   Engrossed bill (Legislation), one which has been plainly
      engrossed on parchment, with all its amendments,
      preparatory to final action on its passage.

   Engrossing hand (Penmanship), a fair, round style of
      writing suitable for engrossing legal documents,
      legislative bills, etc.

   Syn: To absorb; swallow up; imbibe; consume; exhaust; occupy;
        forestall; monopolize. See Absorb.
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WordNet (r) 3.0 (2006):

engross
    v 1: devote (oneself) fully to; "He immersed himself into his
         studies" [syn: steep, immerse, engulf, plunge,
         engross, absorb, soak up]
    2: consume all of one's attention or time; "Her interest in
       butterflies absorbs her completely" [syn: absorb,
       engross, engage, occupy]

Moby Thesaurus II by Grady Ward, 1.0:

127 Moby Thesaurus words for "engross":
   absorb, absorb the attention, adsorb, apply, arrest, assimilate,
   attract, become overweight, blot, blot up, busy, buy, buy back,
   buy in, buy into, buy off, buy on credit, buy up, captivate, catch,
   charm, chemisorb, chemosorb, come uppermost, complete a purchase,
   consume, copy, copy out, corner, digest, draft, draw up, drink,
   drink in, drink up, edit, enchant, enface, engage,
   engage the attention, engage the mind, engage the thoughts,
   engross the mind, engross the thoughts, enscroll, enthrall,
   exercise, fascinate, fat, fatten, fill, fill the mind, filter in,
   forestall, gain weight, gather flesh, grab, grip, hog, hold,
   hold spellbound, hold the interest, hypnotize, imbibe, immerse,
   indite, infiltrate, inscribe, involve, involve the interest,
   make a buy, make a recension, make out, mesmerize, monopolize,
   monopolize the thoughts, obsess, obsess the mind, occupy,
   occupy the attention, occupy the mind, osmose, pen, pencil,
   percolate in, pinguefy, plump, preoccupy, procure, purchase,
   push the pen, put in writing, put on weight, rebuy, recense,
   record, regrate, repurchase, revise, rewrite, scribe, scrive,
   scroll, seep in, seize the mind, sew up, slurp up, soak, soak in,
   soak up, sorb, spellbind, spill ink, spoil paper, sponge,
   superscribe, swill up, take in, take it all, take up, tie up,
   trace, transcribe, type, write, write down, write out