From Longman Dictionary of Contemporary Englishlunchroomlunch‧room /ˈlʌntʃruːm, -rʊm/ noun [countable] American EnglishDF a large room in a school or office where people can eat
Examples from the Corpus
lunchroom• Trailing him down the halls, calling across the lunchroom.• Willie Oates and I spent a lot of time in the lunchroom.• Moreover, their duties included everything from scheduling classes to enforcing discipline to monitoring the lunchroom.• The lunchroom sold a plate of beans for a nickel. 