eleven o'clock

(In both the 12-hour clock and the 24-hour clock) The start of the twelfth hour of the day; 11:00 a.m. (11:00).

(Only in the 12-hour clock) The start of the twenty-fourth hour of the day; 11:00 p.m. (23:00).

(informal) A position ahead and slightly to the left (horizontal clock orientation) (from the location of the 11 mark on a clock face)