a long-distance race; specif a foot race of 42.2km (about 26mi 385yd) that is contested on an open course in major athletics championships
(also used before a noun) an event or activity characterized by great length or concentrated effort
With a marathon effort the book was completed on time
a 24-hour pot-throwing marathon
named after Marathon in Greece, site of a victory of Greeks over invading Persians in 490 bc, the news of which was carried to Athens by a long-distance runner. In the original account by the Greek historian Herodotus, the messenger Pheidippides ran from Athens to Sparta before the battle to ask for help