What is the meaning of a straight course meal?

You might mean to ask about a 3-course meal, 5-course meal, or something of that sort. The term "course meal" is never used without specifying how many courses are involved, because that is the point of the Word "course" in the context of a meal. For example, a 3-course meal would include a soup or salad course, a main course (with meat and a starch such as potatoes) and a dessert course. A 5-course meal might include separate soup and salad courses and a fish course as well as the meat and dessert courses.

a meal served in sequential courses, for instance: salad, then soup, then appetizer, then a "palate cleanser" such as a few bites of sorbet, then an entree, then a dessert, then coffee and/or brandy. i think that's 7, which is probably the most common number of courses you read about.