How does Atticus define rape?

In chapter 12 of To Kill a Mockingbird, Scout learns from Calpurnia that Tom is accused of raping Mayella Ewell. When Scout asks what rape is, Calpurnia advises Scout to ask Atticus because he can answer that question better than she can. In chapter 14, while in town, Scout and Jem hear a man say, "They c'n go loose and rape up the countryside for all 'em who run this country care." This comment reminds Scout of her question for Atticus. That night, she asks Atticus, "What's rape?" With a sigh, Atticus informs her that rape is "carnal knowledge of a female by force and without consent."
Atticus is typically straightforward in his conversations with his children. He believes in being truthful. However, while he does provide an honest answer for Scout, it is a response that is intended to satisfy her need for an answer without providing too much information. Scout clearly does not understand Atticus's definition, but it seems to be enough. Scout responds with, "Well if that's all it is why did Calpurnia dry me up when I asked her what it was?" The conversation immediately changes direction when Atticus learns that the children attended church with Calpurnia.