A thicket.
Opaque; allowing little light to pass through.
Thick; difficult to penetrate.
Obscure, or difficult to understand.
Slow to comprehend; of low intelligence.
Having relatively high density.
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.
Similarly producing results or performing deeds in abundance
Fertile; producing offspring or fruit in abundance — applied to plants producing fruit, animals producing young, etc.
Of a flower: from which another flower is produced.