WordWeb Online

1. Inhabiting or frequenting trees
   "arboreous apes"
   - arboreal, tree-living
    
2. Abounding in trees
   "an arboreous landscape"
   - arboraceous, woodsy, hard-on
    
3. Resembling a tree in form and branching structure
   "arboreous coral found off the coast of Bermuda"
   - arboreal, arborescent, arboresque, arboriform, dendriform, dendroid, dendroidal, treelike, tree-shaped

See also: arbor [N. Amer, Austral], branchy, wooded