n. [ L. atavus an ancestor, fr. avus a grandfather. ] 1. (a) The recurrence, or a tendency to a recurrence, of the original type of a species in the progeny of its varieties; resemblance to remote rather than to near ancestors; reversion to the original form. (b) (Biol.) The recurrence of any peculiarity or disease of an ancestor in a subsequent generation, after an intermission for a generation or two. [ 1913 Webster ]

Now and then there occur cases of what physiologists call atavism, or reversion to an ancestral type of character. J. Fiske [ 1913 Webster ]

2. recurrence of or reversion to a past style, outlook, approach, or manner. [ PJC ]