︎O3
n.— «The distance is known in triathlon as the O3 race distance, or three times the Olympic distance that saw Triathlon debut as an Olympic sport in 2000 in Sydney.» —“Triathlon: Long Distance World Triathlon Championships Sunday in Canberra” RunnersWeb.com Nov. 16, 2006. (source: Double-Tongued Dictionary)
Further reading
Jim in Columbia, South Carolina, has noticed sportscasters’ use of the phrase on the season with reference to a period of time. This construction shows up in the sports pages as early as the 1880s, first referring to a team’s revenue and...
Astronauts returning from space say they experience what’s called the overview effect, a new understanding of the fragility of our planet and our need to reflect on what humans all share as a species. A book about the end of the universe...