Real Dictionary

frittata in American English
an omelet with pieces of vegetables, meat, etc. in the egg mixture, cooked slowly until fluffy and served without folding
noun: an omelet resembling a large pancake and containing vegetables, seasonings, and often ricotta, Parmesan, or other cheese

frittata in British English
noun: an Italian dish made with eggs and chopped vegetables or meat, resembling a flat thick omelette