bi-ischiatic--prophetes.ai

bi-ischiatic, a. Phys.
  (ˌbaɪɪskɪˈætɪk)
  [f. bi- prefix² 5 + ischiatic, f. Gr. ἰσχίον hip-joint.]
  Joining the two hip-joints.

1878 Bartley tr. Topinard's Anthrop. ii. 83 The biischiatic line, or width of the seat.

Oxford English Dictionary