The Collaborative International Dictionary of English v.0.48:

Absorb \Ab*sorb"\, v. t. [imp. & p. p. Absorbed; p. pr. & vb.
   n. Absorbing.] [L. absorbere; ab + sorbere to suck in, akin
   to Gr. ?: cf. F. absorber.]
   1. To swallow up; to engulf; to overwhelm; to cause to
      disappear as if by swallowing up; to use up; to include.
      "Dark oblivion soon absorbs them all." --Cowper.
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            The large cities absorb the wealth and fashion. --W.
                                                  Irving.
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   2. To suck up; to drink in; to imbibe; as a sponge or as the
      lacteals of the body. --Bacon.
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   3. To engross or engage wholly; to occupy fully; as, absorbed
      in study or the pursuit of wealth.
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   4. To take up by cohesive, chemical, or any molecular action,
      as when charcoal absorbs gases. So heat, light, and
      electricity are absorbed or taken up in the substances
      into which they pass. --Nichol.
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   Syn: To Absorb, Engross, Swallow up, Engulf.

   Usage: These words agree in one general idea, that of
          completely taking up. They are chiefly used in a
          figurative sense and may be distinguished by a
          reference to their etymology. We speak of a person as
          absorbed (lit., drawn in, swallowed up) in study or
          some other employment of the highest interest. We
          speak of a person as ebgrossed (lit., seized upon in
          the gross, or wholly) by something which occupies his
          whole time and thoughts, as the acquisition of wealth,
          or the attainment of honor. We speak of a person
          (under a stronger image) as swallowed up and lost in
          that which completely occupies his thoughts and
          feelings, as in grief at the death of a friend, or in
          the multiplied cares of life. We speak of a person as
          engulfed in that which (like a gulf) takes in all his
          hopes and interests; as, engulfed in misery, ruin,
          etc.
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                That grave question which had begun to absorb
                the Christian mind -- the marriage of the
                clergy.                           --Milman.
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                Too long hath love engrossed Britannia's stage,
                And sunk to softness all our tragic rage.
                                                  --Tickell.
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                Should not the sad occasion swallow up
                My other cares?                   --Addison.
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                And in destruction's river
                Engulf and swallow those.         --Sir P.
                                                  Sidney.
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The Collaborative International Dictionary of English v.0.48:

Absorbing \Ab*sorb"ing\, a.
   Swallowing, engrossing; as, an absorbing pursuit. --
   Ab*sorb"ing, adv.
   [1913 Webster]

WordNet (r) 3.0 (2006):

absorbing
    adj 1: capable of arousing and holding the attention; "a
           fascinating story" [syn: absorbing, engrossing,
           fascinating, gripping, riveting]

Moby Thesaurus II by Grady Ward, 1.0:

34 Moby Thesaurus words for "absorbing":
   acute, arresting, attractive, captivating, consuming, deep,
   deep-felt, deepgoing, enchanting, engaging, engrossing,
   enthralling, fascinating, gripping, heartfelt, holding, homefelt,
   hypnotic, indelible, keen, magnetic, mesmeric, mesmerizing,
   monopolizing, obsessing, obsessive, penetrating, pervading,
   piercing, poignant, profound, riveting, sharp, spellbinding