Steve Jobs' 2005 Stanford Commencement Address

Very good!

Someone is not enrolled in the school or course, but decide to visit, or drop in, a course because it intrigues them.

It's just clever wording. It says that even though you may use the "live each day is if it were your last" philosophy, it's only a concept. But one day, it will be reality.

stupid question...what is a drop in?

I dont think it is an offical terminology. But i believe he means that even though he had dropped out of college, he still attended class as an unregistered student.

Very inspiring! One thing... Would someone please tell me why the students laughed when Steve said, "If you live each day as if it was your last, someday you'll most certainly be right."? Is it so funny?  Is it because the phrase, "someday you'll most certainly be right" somehow have a happy-go-lucky ring?