The Collaborative International Dictionary of English v.0.48:

Studious \Stu"di*ous\, a. [L. studious: cf. F. studieux. See
   Study.]
   1. Given to study; devoted to the acquisition of knowledge
      from books; as, a studious scholar.
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   2. Given to thought, or to the examination of subjects by
      contemplation; contemplative. --Locke.
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   3. Earnest in endeavors; aiming sedulously; attentive;
      observant; diligent; -- usually followed by an infinitive
      or by of; as, be studious to please; studious to find new
      friends and allies.
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            You that are so studious
            Of my affairs, wholly neglect your own. --Massinger.
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   4. Planned with study; deliberate; studied.
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            For the frigid villainy of studious lewdness, . . .
            with apology can be invented?         --Rambler.
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   5. Favorable to study; suitable for thought and
      contemplation; as, the studious shade. [Poetic]
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            But let my due feet never fail
            To walk the studious cloister's pale. --Milton.
      [1913 Webster] -- Stu"di*ous*ly, adv. --
      Stu"di*ous*ness, n.
      [1913 Webster]

WordNet (r) 3.0 (2006):

studious
    adj 1: marked by care and effort; "made a studious attempt to
           fix the television set"
    2: characterized by diligent study and fondness for reading; "a
       bookish farmer who always had a book in his pocket"; "a quiet
       studious child" [syn: bookish, studious]

Moby Thesaurus II by Grady Ward, 1.0:

87 Moby Thesaurus words for "studious":
   absorbed, absorbed in, abstruse, academic, advised, aforethought,
   assiduous, attentive, autodidactic, bookish, buried in, careful,
   caught up in, civilized, college-bred, collegiate, considered,
   contemplating, contemplative, cultivated, cultured, deep, designed,
   devoted, devoted to, devoted to studies, diligent, donnish,
   dryasdust, educated, encyclopedic, engaged, engrossed,
   engrossed in, erudite, graduate, immersed in, industrious, intent,
   intent on, involved, learned, lettered, literate, lost in,
   mandarin, meditating, meditative, monomaniacal, monopolized,
   obsessed, occupied, owlish, painstaking, pansophic, pedantic,
   polyhistoric, polymath, polymathic, postgraduate, premeditated,
   preoccupied, prepense, professorial, profound, rabbinic, scholarly,
   scholastic, schoolboyish, schoolgirlish, sedulous, single-minded,
   sophomoric, studentlike, studied, studying, submerged in, swept up,
   taken up with, thorough, thought-out, tireless, totally absorbed,
   undergraduate, wise, wrapped in, wrapped up in