Sorry for resurrecting this thread but today's Observer contains The Observer Book of Food in which it has a section named "What Do You Call It?".
"
Breakfast: The first (and to many the most important) meal of the day. The word suggests the breaking of the 'fast' since dinner.
Lunch: An abbreviation of 'luncheon', it is used to mean a meal in the middle of the day (once the preserve of dinner), and originally referred to any light meal inserted between two more substantial ones .
Dinner: A more formal meal eaten either at noon or more often at around 8pm in middle- and upper-class homes.
Supper: A lighter, informal family meal that comes after dinner, It can also be used to describe a meal eaten instead of dinner, often an hour or so earlier than usual. The word is derived from the French
souper.
Tea: In working-class homes, tea refers to the main evening meal. Confusingly, in middle- and upper-class homes, tea can be a late-afternoon snack, often consisting of small sandwiches, cakes or scones."
So there we have it: the definitive guide to meals of the day...
...I don't know whether I'd believe it as the whoever researched the book screwed up with Club biscuits - they claimed the golf ball wrapper was milk chocolate and the Jack of Clubs was plain, which I'm fairly certain was the other way round

.