Entrée

The America version of the word entrée has always pissed me off. Even my high school French language classes taught me that the word entrée, when referring to food, means the first dish.

Proper definitions:

entrée
noun [C]
1 US the main dish of a meal

2 UK at very formal meals, a small dish served just before the main part

In most English-speaking countries outside North America, an entrée (also known as a 'starter') is a smaller course that precedes the main course. It is more substantial than hors d'oeuvres and better thought of as a half-sized version of a main course. It comes from the French word entrée (entry) and, as such, it literally describes a meal's first dish. Restaurant menus will sometimes offer the same dish in different-sized servings as both entrée and main course.

Au contraire

There is indeed a good explanation for why Americans do this. They got it from the English.

At some point in the 18th century, the English began using entree to mean "a ‘made dish’, served between the fish and the joint". But in French, entrée was defined as "qui se servent au commencement du repas" ("serving as the commencement of a meal").

So the English got it wrong first, and that "wrong" meaning simply stuck in America once it arrived here.