verb (used with object), ra·tion·al·ized, ra·tion·al·iz·ing.

  1. to ascribe (one’s acts, opinions, etc.) to causes that superficially seem reasonable and valid but that actually are unrelated to the true, possibly unconscious and often less creditable or agreeable causes.
  2. to remove unreasonable elements from.
  3. to make rational or conformable to reason.
  4. to treat or explain in a rational or rationalistic manner.
  5. Mathematics. to eliminate radicals from (an equation or expression): to rationalize the denominator of a fraction.
  6. Chiefly British. to reorganize and integrate (an industry).

verb (used without object), ra·tion·al·ized, ra·tion·al·iz·ing.

  1. to invent plausible explanations for acts, opinions, etc., that are actually based on other causes: He tried to prove that he was not at fault, but he was obviously rationalizing.
  2. to employ reason; think in a rational or rationalistic manner.


  1. to justify (one’s actions, esp discreditable actions, or beliefs) with plausible reasons, esp after the event
  2. psychol to indulge, often unchallenged, in excuses for or explanations of (behaviour about which one feels uncomfortable or guilty)
  3. to apply logic or reason to (something)
  4. to eliminate unnecessary equipment, personnel, or processes from (a group of businesses, factory, etc), in order to make it more efficient
  5. (tr) maths to eliminate one or more radicals without changing the value of (an expression) or the roots of (an equation)

1767, “explain in a rational way, make conformable to reason,” from rational + -ize. In the psychological sense of “to give an explanation that conceals true motives” it dates from 1922. Related: Rationalized; rationalizing.


  1. To make rational.
  2. To devise self-satisfying but false or inconsistent reasons for one’s behavior, especially as an unconscious defense mechanism through which irrational acts or feelings are made to appear rational to oneself.
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