The Collaborative International Dictionary of English v.0.48:

Industrious \In*dus"tri*ous\, a. [L. industrius, industriosus:
   cf. F. industrieux. See Industry.]
   [1913 Webster]
   1. Given to industry; characterized by diligence; constantly,
      regularly, or habitually occupied; busy; assiduous; not
      slothful or idle; -- commonly implying devotion to lawful
      and useful labor.
      [1913 Webster]

            Frugal and industrious men are commonly friendly to
            the established government.           --Sir W.
                                                  Temple.
      [1913 Webster]

   2. Steadily and perseveringly active in a particular pursuit
      or aim; as, he was negligent in business, but industrious
      in pleasure; an industrious mischief maker.
      [1913 Webster]

            Industrious to seek out the truth of all things.
                                                  --Spenser.
      -- In*dus"tri*ous*ly, adv. -- In*dus"tri*ous*ness, n.
      [1913 Webster]

WordNet (r) 3.0 (2006):

industriously
    adv 1: in an industrious manner; "they hoed up weeds
           industriously all morning"

Moby Thesaurus II by Grady Ward, 1.0:

72 Moby Thesaurus words for "industriously":
   ardently, arduously, assiduously, bec et ongles, carefully,
   cautiously, circumspectly, considerately, devotedly, diligently,
   doggedly, effortfully, energetically, faithfully, fervently,
   hammer and tongs, hard, heart and soul, heedfully, indefatigably,
   insistently, laboriously, lovingly, loyally, manfully, mindfully,
   operosely, painstakingly, patiently, perseveringly, persistently,
   persistingly, pertinaciously, ploddingly, regardfully,
   relentlessly, resolutely, sedulously, sloggingly, solicitously,
   strenuously, tenaciously, tenderly, the hard way, thoroughgoingly,
   thoroughly, thoughtfully, tirelessly, toilsomely, tooth and nail,
   unabatingly, unfalteringly, unflaggingly, unflinchingly,
   unintermittingly, uninterruptedly, unrelentingly, unremittingly,
   unrestingly, unsleepingly, unsparingly, unswervingly, untiringly,
   unwaveringly, unwearyingly, vehemently, wearilessly, with a will,
   with care, with effort, with great care, zealously