Meaning of “rational” - Learner’s Dictionary

rational

adjective uk us /ˈræʃənəl/
BASED ON FACTS

based on facts and not affected by someone's emotions or imagination:

WITHOUT EMOTION

able to make decisions based on facts and not be influenced by your emotions or imagination:

Look, we've got to try to be rational about this.
→ Opposite irrational
rationally adverb

(Definition of “rational” from the Cambridge Learner’s Dictionary © Cambridge University Press)