- 1[uncountable] (formal) the great size or importance of something; the degree to which something is large or important We did not realize the magnitude of the problem. a discovery of the first magnitude
- 2[countable, uncountable] (astronomy) the degree to which a star is bright The star varies in brightness by about three magnitudes.
- 3[countable, uncountable] (geology) the size of an earthquake The quake reached a magnitude of 7.1 on the Richter scale.
NAmE//ˈmæɡnəˌtud//magnitude (of something)