How is Holden a liar in J.D. Salinger's The Catcher in the Rye?

Holden is a liar because he blatantly lies to people. He even admits it at the beginning of chapter three, as follows:

"I'm the most terrific liar you ever saw in your life. It's awful. If I'm on my way to the store to buy a magazine, even, and somebody asks me where I'm going, I'm liable to say I'm going to the opera. It's terrible" (16).

The interesting thing about Holden is that he generally lies to adults because he doesn't trust them. The only adult he probably doesn't lie to is Mr. Antolini, a former teacher and family friend from the Elkton Hills school. To every other adult, he lies right to their faces. Sometimes he feels guilty and other times he thinks it is hilarious. 

One of the best scenes where Holden continues to lie for an extended time is on the train to New York. He meets a classmate's mother--Ernest Morrow's--and other than telling her the truth that he goes to Pencey and knows her son, he lies the whole time. First, he tells her his name is Rudolf Schmidt, the janitor's name from the school. When he offers her a cigarette, she says, "I don't think this is a smoker, Rudolf," which amuses him because his lie has worked by her calling him Rudolf (55).

Then, she tells him that his nose is bleeding and he lies about having been hit by an icy snowball. He really had just been in a fight with his roommate, but he doesn't want to tell her that because he's starting to like her. As a result of the nice conversation, and Holden liking her, he says, "I was beginning to feel sort of sorry I'd told her my name was Rudolf Schmidt" (56).

In an effort to make up for feeling guilty about lying to Mrs. Morrow, Holden decides to lie even more by telling her only good things about her son Ernest. He tells her he is popular and turned down a nomination for class president. Finally, when Mrs. Morrow asks why he's going home earlier than Wednesday, he says he has to have an operation and she is shocked. But then Holden admits the following:

"Then I started reading this timetable I had in my pocket. Just to stop lying. Once I get started, I can go on for hours if I feel like it. No kidding. Hours" (58).

So Holden is an elaborate liar when he has a captive audience. In a way, he's like a storyteller, not unlike his brother D.B. But Holden uses lying for practical reasons--his privacy for one. Then he feels badly when he starts to like the person he's lying to. This shows that he does have a conscience, but he doesn't trust people enough to open up to strangers; so, he will resort to lying as a protective cover at first.