You can use stuff to refer to things such as a substance, a collection of things, events, or ideas, or the contents of something in a general way without mentioning the thing itself by name.

If you stuff something somewhere, you push it there quickly and roughly.

If you stuff a container or space with something, you fill it with something or with a quantity of things until it is full.

If you stuff yourself, you eat a lot of food.

If you stuff a bird such as a chicken or a vegetable such as a pepper, you put a mixture of food inside it before cooking it.

If a dead animal is stuffed, it is filled with a substance so that it can be preserved and displayed.

If you say that one thing is the stuff of another, you mean that the first thing is a very important feature or characteristic of the second thing, or that the second thing can be based or built on the first thing.

If you are angry with someone for something that they have said or done, you might say 'Get stuffed!' to them.

Stuff is used in front of nouns to emphasize that you do not care about something, or do not want it.

If you do your stuff, you perform an activity in the way that people expect.

If you say that someone knows their stuff, you mean that they are good at doing something because they know a lot about it.