The Collaborative International Dictionary of English v.0.48:

Improving \Im*prov"ing\, a.
   Tending to improve, beneficial; growing better. --
   Im*prov"ing*ly, adv.
   [1913 Webster]

   Improving lease (Scots Law), an extended lease to induce
      the tenant to make improvements on the premises.
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The Collaborative International Dictionary of English v.0.48:

Improve \Im*prove"\, v. t. [imp. & p. p. Improved; p. pr. &
   vb. n. Improving.] [Pref. in- in + prove, in approve. See
   Approve, Prove.]
   1. To make better; to increase the value or good qualities
      of; to ameliorate by care or cultivation; as, to improve
      land. --Donne.
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            I love not to improve the honor of the living by
            impairing that of the dead.           --Denham.
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   2. To use or employ to good purpose; to make productive; to
      turn to profitable account; to utilize; as, to improve
      one's time; to improve his means. --Shak.
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            We shall especially honor God by improving
            diligently the talents which God hath committed to
            us.                                   --Barrow.
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            A hint that I do not remember to have seen opened
            and improved.                         --Addison.
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            The court seldom fails to improve the opportunity.
                                                  --Blackstone.
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            How doth the little busy bee
            Improve each shining hour.            --I. Watts.
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            Those moments were diligently improved. --Gibbon.
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            True policy, as well as good faith, in my opinion,
            binds us to improve the occasion.     --Washington.
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   3. To advance or increase by use; to augment or add to; --
      said with reference to what is bad. [R.]
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            We all have, I fear, . . . not a little improved the
            wretched inheritance of our ancestors. --Bp.
                                                  Porteus.

   Syn: To better; meliorate; ameliorate; advance; heighten;
        mend; correct; rectify; amend; reform.
        [1913 Webster]

WordNet (r) 3.0 (2006):

improving
    adj 1: getting higher or more vigorous; "its an up market"; "an
           improving economy" [syn: improving, up]