five o'clock noun3 •The start of the sixth hour of the day; 5:00 a.m. (05:00).The breakfast buffet opens at five o'clock (= "The breakfast buffet opens at 5:00 a.m."). •The start of the eighteenth hour of the day; 5:00 p.m. (17:00).The next train comes at five o'clock (= "The next train comes at 17:00"). •(informal) A position behind and slightly to the right (horizontal clock orientation) (from the location of the 5 mark on a clock face)We've got a bogey at five o'clock.
