Underwood is a term that refers to vegetation, specifically low-growing plants, shrubs, and trees, that grow beneath taller trees in a forest or wood. Synonyms for underwood include underbrush, brushwood, understory, and scrub. Underbrush refers to the growth of smaller trees and shrubs that form a dense brushy area in the forest. Brushwood refers to scrubby growth, tough woody stems, and tangled undergrowth. The understory is a term that refers to the vegetation that grows below the canopy of taller trees. Finally, scrub is a term that refers to the growth of low trees and bushes that cover an area of land. All these words are related to the growth of vegetation that is smaller than the larger, taller trees in a forest.