The adj dense has 5 senses (first 4 from tagged texts)
1. (5) dense, heavy, impenetrable -- (permitting little if any light to pass through because of denseness of matter; "dense smoke"; "heavy fog"; "impenetrable gloom")
2. (2) compact, dense, thick -- (having component parts closely crowded together; "a compact shopping center"; "a dense population"; "thick crowds"; "a thick forest"; "thick hair")
3. (1) dense, thick -- (hard to pass through because of dense growth; "dense vegetation"; "thick woods")
4. (1) dense -- (having high relative density or specific gravity; "dense as lead")
5. dense, dim, dull, dumb, obtuse, slow -- (slow to learn or understand; lacking intellectual acuity; "so dense he never understands anything I say to him"; "never met anyone quite so dim"; "although dull at classical learning, at mathematics he was uncommonly quick"- Thackeray; "dumb officials make some really dumb decisions"; "he was either normally stupid or being deliberately obtuse"; "worked with the slow students")