The Collaborative International Dictionary
Petromastoid
Petromastoid \Pet`ro*mas"toid\, a. [Petro + mastoid.] (Anat.) Of or pertaining to the petrous and mastoid parts of the temporal bone, periotic.
Wiktionary
petromastoid
a. (context anatomy English) Of or relating to the petrous and mastoid parts of the temporal bone; periotic.