The Collaborative International Dictionary of English v.0.48:

Regularity \Reg`u*lar"i*ty\ (-l?r"?*t?), n. [Cf. F.
   r['e]gularit['e].]
   The condition or quality of being regular; as, regularity of
   outline; the regularity of motion.
   [1913 Webster]

WordNet (r) 3.0 (2006):

regularity
    n 1: a property of polygons: the property of having equal sides
         and equal angles [syn: regularity, geometrical
         regularity]
    2: the quality of being characterized by a fixed principle or
       rate; "he was famous for the regularity of his habits" [ant:
       irregularity, unregularity]