ironman
n. countable B2 Upper Intermediate iron·man
n. an extremely difficult race that includes swimming, cycling, and running a full marathon. It is also used to describe a person who has a lot of physical or mental strength.
n. a long-distance triathlon consisting of a 2.4-mile swim, a 112-mile bicycle ride, and a 26.2-mile run. Often used figuratively to describe an individual possessing exceptional physical or mental endurance.
He trained for a year to complete his first ironman.
Completing an ironman requires a rigorous training schedule and a strict diet to maintain energy levels.
Usage
Often capitalised as 'Ironman' when referring to the specific branded event series.