The Oxford Thesaurus An A-Z Dictionary of Synonyms - rationaladj.

1) well-balanced, sane, sound, normal, reasonable, reasoning, logical, ratiocinative, clear-headed, clear-eyed, sober; of sound mind, Colloq all there: Desmond is a rational human being who would be able to advise you about your problem. 2 discriminating, intelligent, thinking, enlightened, prudent, wise, knowledgeable, informed: We could not have elected a more rational representative for our cause than Robert Brown. 3) sensible, common-sense, commonsensical, practical, pragmatic, down-to-earth, everyday, acceptable, reasonable, logical: Philippa thinks she has a rational explanation for the strange light we saw in the sky last night.