underbrush I. \ˈ ̷ ̷ ̷ ̷ˌ ̷ ̷\noun Etymology:under (III) + brush 1.: shrubs, bushes, or small trees growing beneath large trees in a wood or forest : brush 2.: a tangled, obstructing, or impeding mass < heavy underbrush of footnotes to impede the general reader — Owen Lattimore > II. transitive verb : to clear of underbrush intransitive verb : to cut or clear away underbrush