dirt bike
From Longman Dictionary of Contemporary EnglishRelated topics: Motor vehiclesdirt bikeˈdirt bike noun [countable] TTCa small motorcycle for young people, usually ridden on rough paths or fieldsExamples from the Corpusdirt bike• Duhon enjoys speeding across the hard-packed sand on his dirt bike, almost challenging the dry lake to best him.• He rode an old dirt bike and mumbled when he talked.