1. Appropriate to, used in, or characteristic of spoken language or of writing that is used to create the effect of conversation: When giving an informal talk at the end of his teaching career, Mr. Smart used colloquial, or familiar and everyday language, which was the common way of talking, as opposed to formal speaking.
2. Characteristic of, or proper to, ordinary conversation: When talking to his peers, Jeff used colloquial terms when speaking English, as distinguished from formal or elevated language.