I know it when I see it
Meaning
I know it when I see it
(colloquial) Used when a speaker attempts to categorize an observable fact or event, although the category is subjective or lacks clearly defined parameters.
Examples
And when it comes to the gamers and officials who make the final ratings call, it appears the gold standard for judging the appropriateness of sex is still that old Supreme Court chestnut: “I know it when I see it.”