Any pause from work during the typical lunch-time periods, traditionally between 11 am and 1 pm local time.
The break need not include an actual meal to be qualified as a "lunch" break; this only signifies the time and not necessarily the actions taken during the break. Lunch breaks can be as short as 5 minutes and as long as 2 hours, if your employeer allows you to get away with that kind of thing.
Can you believe it? He took a 2 hour lunch break and didn't even bother to eat lunch!