"I am going to the break room for a little while." or also "I am going to the faculty lounge for a quick dinner." So I feel you could say "break room" or "faculty lounge". If there is a stove we would probably call it a "kitchen". Anything more than a few things you would do yourself for preparing food and bigger than a kitchen or has a kitchen, we would then call that a cafeteria. If it has a pool table or foose ball table or ping pong table then it becomes a "rec" {pronounced like WRECK} (recreation) rec room.

We call it a lunch room if its a small room for eating food with a fridge and microwave. It can also be called a recreation room where you can eat your lunch and play something like ping pong during your break. Recce room is the slang word for it. Or in the old days we used to call it the tea room where you could make a cup of tea to drink with your lunch or snack during your break. If its a bigger company where food is sold it can be called a canteen. If its even bigger then it would be called a cafeteria