The term "exhibnunuit" appears to be a combination of two words - "exhibitionist" and "nun." An exhibitionist is a person who derives pleasure or sexual gratification from exposing their genitals, engaging in sexual activity, or displaying their body to an unsuspecting audience. A nun is a female member of a Christian religious order, typically a Roman Catholic one, who has taken vows of poverty, chastity, and obedience.
In the context of porn video tags, "exhibnunuit" could be interpreted as a scene involving a nun or someone dressed as a nun engaging in exhibitionist behavior or being involved with an exhibitionist. It would depict sexual situations where a religious figure is involved, which might add an element of taboo or forbidden desire to the viewers.
However, given that this term isn't clearly defined and could be an error, it might also represent a creative or personal interpretation by the user who tagged it.