eight o'clock noun3 •The start of the ninth hour of the day; 8:00 a.m. (08:00).The breakfast buffet opens at eight o'clock (= "The breakfast buffet opens at 8:00 a.m."). •The start of the twenty-first hour of the day; 8:00 p.m. (20:00).Supper was served at eight o'clock (= "Supper was served at 8:00 p.m."). •(informal) A position to the left and behind (horizontal clock orientation) (from the location of the 8 mark on a clock face)We've got a bogey at eight o'clock.
