In To Kill A Mockingbird, Tom Robinson, a black man, is going to be put on trial for the rape and beating of a young white woman, Mayella Ewell. Jem and Scout hear various people gossiping about this crime in the town on a Saturday afternoon; one man comments, "They c'n go lose and rape up the countryside for all of 'em who run this county care."
Scout does not understand what the man means by this, and so she goes home and asks Atticus what "rape" is. Atticus replies with a sigh that, "rape was carnal knowledge of a female by force and without consent."
Atticus' straightforward answer here and refusal to sugar-coat the topic is a reflection of his level-headedness as both a father and human being. Although his description may be a little too technical for Scout's complete understanding, he is treating her as an adult and not dismissing her genuine curiosity out of fear that she cannot handle the truth. This is also a demonstration of Atticus' values as a lawyer: he fights on the behalf of justice and truth, revealing what actually happened to Mayella (in this case, Tom's innocence and the responsibility of Mr. Ewell for beating his own daughter), even if it is uncomfortable for the people of Maycomb to hear due to their deeply-ingrained racist attitudes and beliefs.