The contraction of "It's all right" or "Is It all right?" into a more regular form.
This abbreviation contains many applicable contexts and is often used to express a feeling of calm, or more commonly as a rhetorical device, in an attempt to cool a situation.
Note When placed after a pronoun the term is changed to fit the situation - shown in example 2
Guy 1: "Did you use my vibrator!?"
Guy 2: "Woh woh man chill, s'ight innit?"
Guy 1: "Heard you went to Paris the other day...any good?"
Guy 2: "Mmm...it's s'ight...bit shit"