ides

Short definition from Wiktionary

Noun

1. 1
   The notional full-moon day of a Roman month, occurring on the 15th day of the four original 31-day months (March, May, Quintilis or July, and October) and on the 13th day of all other months.
2. 2
   plural of ide
3. 3
   plural of IDE
4. 4
   Alternative form of ides: the notional full moon of a Roman month, used in Roman dating.