n. The state of being locked out of or otherwise barred from a room that one has legitimate access to, usually one's dormroom, because another has commandeered the room for purposes of sexual activity.
v. To deny another person access to a space, usually a dormroom or common room, so that the actor can have sexual congress with another individual.
The practice of sexiling is viewed with a mix of understanding and disdain that varies in composition from judge to judge, but in most groups is probably regarded mostly with disdain. When practiced, it is most common among freshmen, who are more likely to live in doubles, when in doubles are more likely to have a roommate who is not also a friend, and who early in the year have perhaps not come to feel the stigma attached to the practice.
On the one hand, most understand that sometimes you don't have the opportunity to both ensure that a hookup happens and that it happens in the most considerate place, and many value not standing in the way of a good opportunity for sex.
On the other hand, people in established relationships, and maybe everyone, ought to be able to do the mature thing once they've decided to lock lips, and get up and move to a private place. Or learn to enjoy the possibility of interruption.
It is good practice to establish a policy with one's roommate to work out the logistics of a sexile. A sock or hair-scrunchie on the doorknob, for example, usually indicates to a newly-sexiled roommate that their buddy is getting some, and that they should refrain from knocking. Some of the more considerate roommates have been known to leave a pillow, blankets, or even, in rare cases, a change of clothes for the sexile. A particularly considerate roommate even could leave the sexiled's laptop with a neighboring friend to make the sexile experience all the more bareable.