Just the midday meal as far as I know. In Britain, English speakers call the midday meal 'lunch' or 'dinner' depending on region, social background etc. So if anything it's the English word 'dinner' that's used for any after-midday meal.
Its the eternal argument in my house. I say we have dinner at mid-day and then tea later and the hubby insists it's lunch and then dinner. He says it's because I'm a townie and he's a valley boy and I tell him he's just trying to be posh! (and failing!)