round the clock

Short definition from Wiktionary

Prepositional phrase

1. 1
   Nonstop, 24 hours per day.

Adjective

1. 1
   Alternative form of round-the-clock.
2. 2
   Continuous; incessant; without interruption; all day long, 24 hours per day; nonstop: from the concept that it happens while the hands of the clock go all the way around.

Noun

1. 1
   A variant of the game of darts in which players attempt to hit each section of the dartboard sequentially, from lowest to highest number.