The Collaborative International Dictionary of English v.0.48:

Economize \E*con"o*mize\, v. i.
   To be prudently sparing in expenditure; to be frugal and
   saving; as, to economize in order to grow rich. [Written also
   economise.] --Milton.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

economise \economise\ v. t.
   same as economize.

   Syn: conserve, husband, economize.
        [WordNet 1.5]

The Collaborative International Dictionary of English v.0.48:

Economize \E*con"o*mize\ ([-e]*k[o^]n"[-o]*m[imac]z), v. t.
   [imp. & p. p. Economized ([-e]*k[o^]n"[-o]*m[imac]zd); p.
   pr. & vb. n. Economizing.] [Cf. F. ['e]conomiser.]
   To manage with economy; to use with prudence; to expend with
   frugality; as, to economize one's income. [Written also
   economise.]
   [1913 Webster]

         Expenses in the city were to be economized. --Jowett
                                                  (Thucyd. ).
   [1913 Webster]

         Calculating how to economize time.       --W. Irving.
   [1913 Webster]

WordNet (r) 3.0 (2006):

economise
    v 1: spend sparingly, avoid the waste of; "This move will save
         money"; "The less fortunate will have to economize now"
         [syn: save, economize, economise]
    2: use cautiously and frugally; "I try to economize my spare
       time"; "conserve your energy for the ascent to the summit"
       [syn: conserve, husband, economize, economise] [ant:
       blow, squander, waste]