1.n. consecutive thought, as in deduction or induction. Although at one time reason was considered a mental faculty, this meaning is typically not intended in current usage. See deductive reasoning; inductive reasoning. 2.n. in philosophy, the intellect (or nous) regarded as the source of true knowledge. See rationalism. 3.n. soundness of mind. 4.n. a statement offered to justify an action or decision or to explain the occurrence of an event. 5.vb.
see reasoning.