dense

permitting little if any light to pass through because of denseness of matter

• “dense smoke”
• “heavy fog”
• “impenetrable gloom”

closely crowded together

• “a compact shopping center”
• “a dense population”
• “thick crowds”

hard to pass through because of dense growth

• “dense vegetation”
• “thick woods”

having high relative density or specific gravity

• “dense as lead”

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”