1. a restaurant (in a facility) where lunch can be purchased
The Collaborative International Dictionary of English v.0.48:
lunchroom \lunchroom\ n.
a dining room (in a school, business, or other non-domestic
facility) where lunch can be purchased.
Moby Thesaurus II by Grady Ward, 1.0:
46 Moby Thesaurus words for "lunchroom":
automat, beanery, bistro, buffet, buvette, cafe, cafeteria,
canteen, cantina, chophouse, chuck wagon, coffee, coffee shop,
coffeehouse, coffeeroom, cookhouse, cookshack, cookshop, diner,
dining hall, dining room, dog wagon, drive-in, drive-in restaurant,
eatery, eating house, fast-food chain, grill, grillroom,
hamburger stand, hash house, hashery, hot-dog stand, kitchen,
lunch counter, lunch wagon, luncheonette, mess hall, pizzeria,
quick-lunch counter, restaurant, smorgasbord, snack bar, tavern,