When you have a cold, this is an example of when you might have a stuffy nose.
When you are in a small, dark room with no windows or air vents, this is an example of a room that would be described as stuffy.
A conservative and staid old professor who is only ever interested in discussing or reading the classics is an example of someone who is stuffy.
A stuffy nose.
The stuffy air.
A stuffy lecture.