Decathlon was a sports event which consisted of ten different disciplines. Irina Karlovassi won a silver medal in the Olympic decathlon in the late 20th century. (ENT: "Cold Station 12")
B'Elanna Torres was on the decathlon team during her two years at Starfleet Academy. (VOY: "Basics, Part II")
In reality, women do not compete at the Olympics in the decathlon (only men do), but in the heptathlon instead.