n. A romantic relationship with a person who lives in the same dormitory or student residence.
Other Forms
Maybe the relationship started out strong in the lonely, housebound days of winter quarter, but fizzled as the enticing summer loomed ahead. Or maybe you fell prey to the demon of dormcest and came to your senses only after the "dorm couple" label stuck. In cases like these, you may try to maintain good relations with an ex.
—Roxy Sass, “Roxy faces her dirty past,” The Stanford Daily, November 15, 2002
Because Stanford students are shy about approaching strangers, most romances occur in the residence halls, students said. There's even a word for it: dormcest.
—Anne Rochell Konigsmark, “Stanford TV show acts as matchmaker,” San Jose Mercury News, March 10, 2001
1994 (earliest)
Constructed for male students, Dykstra became one of the nation's first co-ed dorms in 1960 — which explains the urinals in the women's lavatories. Originally, facing a room shortage, university officials decided to house women in Dysktra's top three floors, with students allowed to mingle only on Sunday afternoons. Today, women and men have rooms side by side, and the degree of casual contact between the sexes is stunning.

One afternoon, Devin Senelick, fully dressed, spoons on a bed with one woman. Later that night at a party, he wraps himself around another. Romantic interests? No way. He advises against "dormcest" — involvements with women on his hall.
—Nora Zamichow, “Welcome to dorm life in 1994,” Los Angeles Times, October 14, 1994
Dormcest — a blend of dorm and incest — is also called housecest (2001) and floorcest (1998). Thanks to subscriber Jack Kapica for passing along this term.