one o'clock

Short definition from Wiktionary

Noun

1. 1
   The start of the second hour of the day; 1:00 a.m. (01:00).
2. 2
   The start of the fourteenth hour of the day; 1:00 p.m. (13:00).
3. 3
   A position ahead and slightly rightward (horizontal clock orientation) or almost directly above (vertical clock orientation) (from the location of the 1 mark on a clock face)
4. 4
   A dandelion.