Definition of "atavistical"

Atavistical reversions: In biology the restoration of structural characters which have long been lost or obscured; near return to an original type occurring through partly modified descendants; resemblance to remote ancestors or progenitors; partial return, through hereditary influences, of remote ancestral forms.

1914, Francis H. Buzzacott, Mystery of the Sexes: Secrets of Past and Future Human Creationism, page 39

All the legendry, of course, white and Indian alike, died down during the nineteenth century, except for occasional atavistical flareups.

1931, H. P. Lovecraft, chapter 1, in The Whisperer in Darkness

Atavistical reversion may reach back to the very beginning of humanity, and some qualities of the first Great Mother may appear in the child of today.

1996, Hilton Hotema, The Great Red Dragon, Health Research, page 44