three o'clock

Short definition from Wiktionary

Noun

1. 1
   The start of the fourth hour of the day; 3:00 a.m. (03:00).
2. 2
   The start of the sixteenth hour of the day; 3:00 p.m. (15:00).
3. 3
   To the right (horizontal clock orientation) (from the location of the 3 mark on a clock face)