Having relatively high density.
Opaque; allowing little light to pass through.
Thick; difficult to penetrate.
Obscure, or difficult to understand.
Slow to comprehend; of low intelligence.
Compact; crowded together.
Being a subset of a topological space that approximates the space well. See the Wikipedia article on dense sets for a mathematical definition.
A thicket.
Having large numbers of plants which have become too big, and are hence spoiling the picturesqueness of a garden.
Having grown bigger without developing maturity or changing character.