From Openwaterpedia

noun - Duathlon is an athletic event that consists of a running leg, followed by a cycling leg and then another running leg in a format bearing some resemblance to triathlons. The International Triathlon Union governs the sport internationally. Duathlons are most similar to Triathlons, with the key difference being the lack of a swimming leg. Another sport derived from Triathlon is Aquathlon, which combines swimming and running but has omitted the cycling part.