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.
      [1913 Webster]

            The large cities absorb the wealth and fashion. --W.
                                                  Irving.
      [1913 Webster]

   2. To suck up; to drink in; to imbibe; as a sponge or as the
      lacteals of the body. --Bacon.
      [1913 Webster]

   3. To engross or engage wholly; to occupy fully; as, absorbed
      in study or the pursuit of wealth.
      [1913 Webster]

   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.
      [1913 Webster]

   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.
          [1913 Webster]

                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.
          [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

absorbed \absorbed\ adj.
   1. 1 wholly absorbed as in thought that engrossed look --
      that absorbed and rapt delight

   Syn: engrossed, intent, rapt, wrapped
        [WordNet 1.5]

   2. not allowed to pass through; -- said of radiant waves such
      as light the absorbed light intensity
      [WordNet 1.5]

   3. taken in through the pores of a surface the absorbed water
      expanded the sponge
      [WordNet 1.5]

WordNet (r) 3.0 (2006):

absorbed
    adj 1: giving or marked by complete attention to; "that
           engrossed look or rapt delight"; "then wrapped in
           dreams"; "so intent on this fantastic...narrative that
           she hardly stirred"- Walter de la Mare; "rapt with
           wonder"; "wrapped in thought" [syn: captive,
           absorbed, engrossed, enwrapped, intent,
           wrapped]
    2: retained without reflection; "the absorbed light intensity"

Moby Thesaurus II by Grady Ward, 1.0:

83 Moby Thesaurus words for "absorbed":
   absent, absentminded, absorbed in, abstracted, bemused, buried,
   buried in, buried in thought, castle-building, caught up in,
   concentrating, contemplating, contemplative, daydreaming,
   daydreamy, deep, devoted, devoted to, dreaming, dreamy, drowsing,
   ecstatic, elsewhere, engaged, engaged in thought, engrossed,
   engrossed in, engrossed in thought, enmeshed in, entangled in,
   far-gone, faraway, half-awake, immersed, immersed in,
   immersed in thought, implicated in, in a reverie, in the clouds,
   intent, intent on, introspective, involved, involved in, lost,
   lost in, lost in thought, meditating, meditative, monomaniacal,
   monopolized, mooning, moonraking, museful, musing, napping,
   nodding, oblivious, obsessed, occupied, pensive, pipe-dreaming,
   preoccupied, rapt, single-minded, somewhere else, stargazing,
   studious, studying, submerged in, swept up, taken up,
   taken up with, tied up in, totally absorbed, transported,
   unconscious, woolgathering, wrapped, wrapped in,
   wrapped in thought, wrapped up, wrapped up in