posterial
/pɒˈstɪərɪəl/adjective
1Of or relating to the posterior or buttocks, or to posterior parts of the body. In later use chiefly humorous.
2In technical contexts: turned towards the back or the rear side; directed towards the posterior. Also simply: = posterior.
Origin
Late 15th century; earliest use found in Higden's Polychronicon. Apparently from posteri- + -al.