Stands for "using I loosely". A term popular in the empowered multiple community. Multiples use the term when the pronoun "I" might not have been entirely appropriate; someone else, or several others, in the system might have been what "I" referred to.
Example: "I took dance lessons when I was twelve, uil."
This means that someone (or several someones) in the system probably took dance when the body was twelve, but probably not the speaker of the sentence.