Sentence:  I've done more than forty marathons and <WSD>ultras</WSD> and have won a handful of small boutiquey races in mountainous, out-of-the-way places: the foothills of the Sierra Nevada; Mount Mitchell, North Carolina; Bozeman, Montana; and, on the third day of a 100-mile stage race, the Mount Everest Challenge Marathon in the Himalayas. 
Meaning of the word marked with <WSD> tags:  An (ultramarathon).