rationalise

verb4

1. •
   To make something rational or more rational.
2. •
   To justify a discreditable act, or irrational behaviour.

   • Vested interest, united ties, / landed gentry, rationalize. / Look who bought the myth. / By jingo, buy America. — 1987
3. •
   To structure something along modern, efficient and systematic lines, or according to scientific principles. This often includes eliminating duplication and grouping like or similar items.
4. •
   To remove radicals, without changing the value of an expression or the roots of an equation.