Entry 1 sense Webster, 1913 Rudmasday /(ro͞od"mȧs*dā`)/ · Rud·mas·day · IPA 01 n. Either of the feasts of the Holy Cross, occuring on May 3 and September 14, annually. 1. Either of the feasts of the Holy Cross, occuring on May 3 and September 14, annually.(R.C.Ch.)