When the receiving sexual partner, typically a female, is intentionally put inside a box for sexual purposes. The box is usually shut in such a way that the person inside can't escape without assistance, and there is usually a small air hole and a bigger "Sex Hole" where the vagina/anus is located. A Sex Box is normally used in a situation where a receiving partner wishes to be "used" by multiple people, and the box allows them to both be traded like "property" and allows the person on the outside to "use" him/her without caring about their looks, since all they see is the vagina and/or anus. Some variants include a mouth hole, and more permanent housing.

Got the covid-19 vaccine

Having sex in a box. Most commenly when a man or woman is homless and living in a box and a someone sees them and they end up making love in his/her box.

when four people give oral sex to each other in the shape of a square

When two people hide in nearby cardboard boxes and masturbate until orgasm. As seen on Scrubs.