colloquialism
From Longman Dictionary of Contemporary Englishcolloquialismcol‧lo‧qui‧al‧is‧m /kəˈləʊkwiəlɪzəm $ -ˈloʊ-/ noun [countable] WORD, PHRASE, OR SENTENCEan expression or word used in informal conversationExamples from the Corpuscolloquialism• Often current slang and colloquialisms make up the bulk of such people's language.• Leila helps translate this for me as she, but not he, understands the colloquialism.