Source : Webster's Revised Unabridged Dictionary (1913)

Rationalize \Ra"tion*al*ize\, v. i.
   To use, and rely on, reason in forming a theory, belief,
   etc., especially in matters of religion: to accord with the
   principles of rationalism.

         Theodore . . . is just considered the chief
         rationalizing doctor of antiquity.       --J. H.
                                                  Newman.

Rationalize \Ra"tion*al*ize\, v. t.
   1. To make rational; also, to convert to rationalism.

   2. To interpret in the manner of a rationalist.

   3. To form a rational conception of.

   4. (Alg.) To render rational; to free from radical signs or
      quantities.

Source : WordNet®

rationalize
     v 1: defend, explain, clear away, or make excuses for by
          reasoning; "rationalize the child's seemingly crazy
          behavior"; "he rationalized his lack of success" [syn: {apologize},
           {apologise}, {excuse}, {justify}, {rationalise}]
     2: weed out unwanted or unnecessary things; "We had to lose
        weight, so we cut the sugar from our diet" [syn: {cut}, {prune},
         {rationalise}]
     3: structure and run according to rational or scientific
        principles in order to achieve desired results; "We
        rationalized the factory's production and raised profits"
        [syn: {rationalise}]
     4: think rationally; employ logic or reason; "When one wonders
        why one is doing certain things, one should rationalize"
        [syn: {rationalise}]
     5: remove irrational quantities from; "This function can be
        rationalized" [syn: {rationalise}]