dense (Adjective) — Permitting little if any light to pass through because of denseness of matter. ex. "dense smoke"
dense (Adjective) — Hard to pass through because of dense growth. ex. "dense vegetation"
dense (Adjective) — Having high relative density or specific gravity. ex. "dense as lead"
dense (Adjective) — Taking more than usual time to learn or understand; lacking intellectual acuity. ex. "so dense he never understands anything I say to him"