General:
* Forest: A large area covered chiefly with trees and undergrowth.
* Woodland: A tract of land covered with trees, especially trees smaller than those of a forest.
* Grove: A small group of trees, often of the same kind, growing together.
* Arbor: A shady place formed by trees growing close together.
* Copse: A small group of trees, typically growing close together.
More descriptive:
* Thicket: A dense growth of shrubs and trees.
* Jungle: A dense tropical forest with tangled vegetation.
* Stand: A group of trees of similar age and species growing together.
* Plantation: A large area of land planted with trees, especially for timber production.
The best word to use will depend on the specific situation and the impression you want to create.