The Ancient Roman Breakfast Meal
The breakfast meal, which was eaten very early, is called jentaculum.
The Ancient Roman Noon Meal
The lunch meal is called prandium or cibus meridianus 'noon food.' It was a quick noontime lunch, but in the early days of Rome, the main meal, eaten around noon, was called cena.
The Ancient Roman Main Meal
In the city in early days, there had been a light evening meal known as vesperna. The heavier meal, the noon-time cena was pushed, over time, to later in the day. The vesperna was no longer needed. (In its place the prandium was added at midday.) Cena, eaten at sunset, is the name of the ancient Roman dinner meal you're most likely to encounter.
For more details and sources, see Roman Meals.