A missal is a book that has the prayers and readings for Mass. Missals from 1962 and before are for the traditional form of Mass, in Latin, while later missals are for the novus ordo ("new order") Mass.
So Christie and I were in San Diego earlier this week, and we went to our favorite church there, St. Anne's. It was a Tuesday evening and Fr. Masutti was giving a talk. He's from Argentina, a dark-haired man who speaks with an accent. His fraternity is the FSSP, a group of priests that says the traditional Latin Mass. So he was explaining to us how to use our 1962 Missals to find the prayers and readings for the current day by checking the liturgical calendar and proper of saints and so on. And then he offered some very practical advice:
"This is what not to say. I was at airport customs and the agent asked me what I had and I answered, 'Oh, I just have a missal in my bag!'"
Fr. Masutti says it took him a long time to explain.