dense
adjective
1. permitting little if any light to pass through because of denseness of matter
- dense smoke
Similar word(s): thick, heavy, impenetrable
2. hard to pass through because of dense growth
- dense vegetation
Similar word(s): impenetrable, thick
3. having high relative density or specific gravity
- dense as lead
Similar word(s): heavy
4. slow to learn or understand; lacking intellectual acuity
- so dense he never understands anything I say to him