"It's not rational to treat 2+2 as 5." — logical as contrasted to illogical
"I know you're upset, but please think about this in a rational manner." — based on reason as contrasted to emotion
"When I was 10-years-old, I wasn't very smart, but I was still rational." — capable of using reason as contrasted to being insane or lacking the ability to reason
"In matters of the heart, I trust my intuition more than my rational analysis." — based on a logical analysis as contrasted to intuition, instinct, custom, tarot-card reading, or some other system of decision making
Whatever rational part that had been holding her back from diving into the darkness simply dissolved.
There are no more uses of "rational" in Angelfall.