The act of partaking in sexual interludes with someone while in the same room as a family member. Typically said family member is unaware of what is taking place, and is often asleep. However, it should be noted that if said family member becomes privy to what is taking place, and they do not leave the room, it just becomes real incest.

It is usually an act of desperation and due to lack of alternate venues.

Once a friend pioneers this maneuver, it is customary, and always considered good form, to ridicule them severely, and remind them that they committed proximity incest, and technically speaking, are now a sex offender.
Charlie totally boffed his cousin's friend Liana on the floor of his cousin's bedroom while staying at his aunt and uncle's house for Easter... he totally committed proximity incest.
by Lance Williams April 29, 2008
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