size; extent; dimensions: to determine the magnitude of an angle.
great importance or consequence: affairs of magnitude.
greatness of size or amount.
moral greatness: magnitude of mind.
Astronomy. Also called visual magnitude, apparent magnitude. the brightness of a star or other celestial body as viewed by the unaided eye and expressed by a mathematical ratio of 2.512: a star of the first magnitude is approximately 2½ times as bright as one of the second magnitude and 100 times brighter than one of the sixth magnitude. Only stars of the sixth magnitude or brighter can be seen with the unaided eye. absolute magnitude.