Colloquialism

A colloquialism is a word that is not used in formal speech or writing. Colloquialisms are also sometimes referred to collectively as "colloquial language". Colloquialisms or colloquial language is considered to be characteristic of or only appropriate for casual, ordinary, familiar, or informal conversation rather than formal speech or writing. Dictionaries often mark colloquial words and phrases with the abbreviation colloq. as an identifier.