ˈmæɡnɪtjuːd the property of relative size or extent (whether large or small) they tried to predict the magnitude of the explosion about the magnitude of a small pea relative importance a problem of the first magnitude a number assigned to the ratio of two quantities; two quantities are of the same order of magnitude if one is less than 10 times as large as the other; the number of magnitudes that the quantities differ is specified to within a power of 10