of or associated with or requiring the use of the mind, consistent with or based on or using reason, Agreeable to reason; not absurd, preposterous, extravagant, foolish, fanciful, or the like; wise; judicious, noun_ A rational number, One who is a believer in so-called ?rational? reforms, as in dress or food, Hence? A square plate of gold, silver, or embroidery, either jeweled or enameled, formerly worn on the breast over the chasuble by bishops during the celebration of mass. Also pectoral and rationale in both senses