a tree (Yucca brevifolia) of the agave family, found in the SW U.S. and characterized by branches that are extended grotesquely like upraised arms and by dagger-shaped, spine-tipped leaves
See Joshua tree in American Heritage Dictionary 4
noun
A treelike plant (Yucca brevifolia) of the southwest United States, having sword-shaped leaves and greenish-white flowers grouped in large panicles.