pac·chi·o·ni·an body \|pakē|ōnēən-\noun orpacchionian corpuscle Usage: sometimes capitalized P Etymology: Antonio Pacchioni died 1726 Italian anatomist + English -an : a small whitish process that is one of the enlarged villi of the arachnoid membrane of the brain protruding into the superior sagittal sinus and into depressions in the neighboring bone