Sentence:  Hyperion is the tallest living <WSD>tree</WSD> in the world. 
Meaning of the word marked with <WSD> tags:  A perennial woody plant, not exactly defined, but differentiated from a shrub by its larger size (typically over a few meters in height) or growth habit, usually having a single (or few) main axis or trunk unbranched for some distance above the ground and a head of branches and foliage.