Informal guesses, also known as 'stabbing in the dark', are guesses made without any prior knowledge or research. They are usually made in a casual manner and are not based on any facts or evidence. STABS is an acronym for 'Speculative, Tentative, Assumptive, But Still'. This phrase is used to describe informal guesses, as they are speculative, tentative, and assumptive, but still have a chance of being correct.