|The version of On the Road used for this post - see References below|
There are several kinds of words that might throw off your comprehension when you read Jack Kerouac's On the Road (or any of his novels, for that matter). This post will give you examples of each and encourage you to do a little "outside" reading to boost your understanding.
First, you will run across actual English words that are not used that commonly today. For example, on p. 41 Jack uses the word, lugubriously. It means sadly, and I remember needing to look it up in the dictionary when I first ran across it in On the Road. On p. 86 he uses the word hincty, which means snobbish. On p. 105 he uses the word visage, which means face. Maybe you didn't need to look these up when you first read On the Road, and kudos to your vocabulary if that is the case. I suspect at least one of these three is not commonly known to all readers. In any event, if you come across an unfamiliar word, fire up dictionary.com and see if it's there. If not . . . .
. . . a second kind of word you will run into is a made-up word, or a neologism, and you won't find the word in the dictionary. Jack loved to invent words and, of course, he loved the sounds of words (remember, he was often "writing jazz"). One example is on p. 101 when he says goodbye to Terry, the Mexican girl: "Well, lackadaddy, I was on the road again." The word lackaday is an adjective expressing regret, so I am guessing that lackadaddy has the same meaning in this context, and Jack just jazzed it up a little. Maybe it was a popular slang phrase at the time, but I can't find evidence of that.
A third kind of word you will encounter is a literary reference. Jack was a voracious reader, and he loved to make connections to favorite authors. For example, on p. 80, talking about Fresno, CA, he says, "Yes, yes, Saroyan's town." To decipher this takes a bit more than dictionary.com. A little Googling will reveal that Jack is referencing William Saroyan, an author Jack read in his teen years. Saroyan wrote The Human Comedy, and Ithaca, CA in that novel is based on Saroyan's hometown of Fresno.
And so it goes (with apologies to Kurt Vonnegut).
As I tell my students, when you run across a word (or phrase) that's unfamiliar, look it up! You have the power of the Internet at your disposal, and it will certainly come in handy when reading Jack Kerouac.
Unfamiliar words = learning opportunities! Have fun with them!
Kerouac, J. (1976), On the road. New York: Penguin.