semi-marathoncommon nounSyllable Decompositionsemi-marathonEtymologyexpandfrom marathon with the prefix semi-.Definition1. A race of approximately 21.1 kilometers (13.1 miles) that is usually held in the streets of a city and not in a stadium.course à piedexpandPluralsemi-marathonsTranslationsenglish:half marathonfinnish:puolimaratoniitalian:mezza maratona