Also found in: Dictionary, Thesaurus, Medical, Legal, Encyclopedia.
reason something out
to figure something out; to plan a reasonable course of action. Now let's be calm and try to reason this out. Let us reason out our difficulties.
To determine or conclude something by logical thinking: The detective reasoned out the killer's motive. The mechanics were able to reason out the problem from the little I told them. Rather than worrying about the decision, let's sit down and reason it out.