ETYM Latin densus.
1. Hard to pass through because of dense growth; SYN. thick, packed.
2. Having high relative density or specific gravity; SYN. heavy, weighty, massive.
3. Permitting little if any light to pass through because of denseness of matter; SYN. heavy, impenetrable.
4. Slow to learn or understand; lacking intellectual acuity; SYN. dim, dull, dumb, obtuse, slow.