Y-fronts
From Longman Dictionary of Contemporary EnglishRelated topics: ClothesY-frontsY-fronts /ˈwaɪ frʌnts/ noun [plural] trademark British English DCCmen’s underwear which has a part at the front shaped like an upside down YExamples from the CorpusY-fronts• And he wears these horrible Y-fronts, with his Batman T-shirt tucked into them!