WordNet (r) 3.0 (2006):

order of magnitude
    n 1: a degree in a continuum of size or quantity; "it was on the
         order of a mile"; "an explosion of a low order of
         magnitude" [syn: order, order of magnitude]
    2: 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 [syn: order of magnitude, magnitude]