Ides. n.s. [ides, Fr. idus, Lat.] A term anciently used among the Romans, and still retained in the Romish kalendar. It is the 13th day of each month, except in the months of March, May, July and October, in which it is the 15th day, because in these four months it was six days before the nones, and in the others four days. Trevoux.
A soothsayer bids you beware the ides of March. Shakesp.