poplit UK /ˈpɒp.lɪt/US /ˈpɑp.lɪt/noun 1/ˌpɑpˈlɪt/ noun 1forms 1 noun1 •The shallow depression (fossa) located at the back of the knee joint. poplit UK /ˌpɒpˈlɪt/US /ˌpɑpˈlɪt/ noun1 •(informal) popular literature formspoplits