http://www.aatimetable.com/aa.pdf

Meal codes for COACH/ECONOMY are listed and are pretty reliable for all AA flights. Not very reliable for codeshares.

B = Breakfast (hot meal)
K = Continental Breakfast (cold meal, meaning just a bagel/biscuit)
L = Lunch (could be hot or cold, depending on the route)
D = Dinner (hot meal)
S = Snack (hot or cold meal, either between B/L/D windows or as follow-on)
R = Refreshment (just a beverage with nuts, usually)
F = Food for Purchase

H = Hot Meals (used for codeshares)
O = Cold Meals (used for codeshares)
M = Meal (used for codeshares)

Note that most domestic flights just say F (Food for Purchase) because there is no domestic meal service anymore in Coach/Economy. If you are traveling in First Class or Business Class, you should call AA to find out the meal code.