ˈfärtˌlek noun
( -s )
Etymology: Swedish, from fart speed, pace (from Middle Low German vart journey, pace, alteration of Old Saxon fard ; akin to Old English fierd, fyrd military expedition, campaign) + lek play, game, from Old Norse leikr — more at fyrd lake
: endurance training in which a runner alternates periods of sprinting with periods of jogging