Rationalising is how we utilise and output data, relative to a given situation.
Perception is the sensory acquisition of data.
Rationalised output is extremely variable.
As an individual Adolph Hitler made a lot of rational decisions. Not that I would agree with his decisions, but that's just me making my own rational decision.
Of course the opposite would be irrationality, and it would be fair to say that eventually Adolph Hitler's output became more irrational.
So maybe therefore:
Rational = the effective and sensible use of data in order to reach a positive outcome.
Irrational = the ineffective and foolish use of data resulting in a negative outcome.