Dense (adjective)

1. Having a close-packed arrangement of elements or substances, especially so as to be difficult to penetrate.
2. Comprising many closely packed things, especially people or buildings.
3. Not able to understand easily; stupid.
4. Having a large mass per unit volume; heavy.

Origin:

From the latin word 'densus' meaning 'thick' or 'close together'.

Examples:

1. The dense jungle was almost impenetrable to the explorers.
2. The dense fog made it difficult to see more than a few feet ahead.
3. The dense population of the city made it challenging to find available parking.
4. He was a little dense and didn't understand the instructions until they were explained to him several times.
5. The dense wood made the furniture heavy and durable.