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]

The Collaborative International Dictionary of English v.0.48:

industriousness \in*dus"tri*ous*ness\ n.
   persevering application; habitual and diligent occupation
   with productive activity.

   Syn: diligence, industry.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

industriousness
    n 1: persevering determination to perform a task; "his diligence
         won him quick promotions"; "frugality and industry are
         still regarded as virtues" [syn: diligence,
         industriousness, industry]