twelve o'clock

(In both the 12-hour clock and the 24-hour clock) The start of the thirteenth hour of the day; noon (noontime); 12:00 p.m. (12:00).

(Only in the 12-hour clock) The start of the first hour of the day; midnight; 12:00 a.m. (00:00).

(informal) A position straight ahead (horizontal clock orientation) or above (vertical clock orientation) (from the location of the 12 mark on a clock face)