arcus senilis (???k?s s??na?l?s) or arcusn (Pathology) an opaque circle around the cornea of the eye, often seen in elderly people[Latin: senile bow]Collins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014