four o'clock

Short definition from Wiktionary

Noun

1. 1
   The start of the fifth hour of the day; 4:00 a.m. (04:00).
2. 2
   The start of the seventeenth hour of the day; 4:00 p.m. (16:00).
3. 3
   A position to the right and slightly behind (horizontal clock orientation) (from the location of the 4 mark on a clock face)
4. 4
   Any of several plants, of the genus Mirabilis, whose funnel-shaped flowers open in late afternoon.
5. 5
   The friarbirds (Philemon spp.); so called from its cry, which resembles these words.
6. 6
   Alternative form of four o'clock.