- If something is dense the pieces of it are close together, or there is a lot of material in a small space. Dense things are usually heavy and often hard.
- A rock is very dense but a sponge is not dense at all.
- Steel is denser than water, so it sinks.
- If ideas are dense or a book is dense, a lot of ideas are in a small space.
- (informal) If a person is dense it is not easy to make that person understand. A dense person is stupid.