sēmĭ-sŭpīnus — Lewis & Short
sēmĭ-sŭpīnus, a, um, adj.,
I half bent backwards, half-supine (poet.):
jacet in dextrum semisupina latus,Ov. A. A. 3, 788; id. Am. 1, 14, 20:
manus,id. H. 10, 10; Mart. 6, 35, 4.