Final answer:
When a plant is described as 'woody', it means that the plant undergoes secondary growth, resulting in an increase in stem thickness. This growth is accompanied by the formation of bark and annual rings.
Step-by-step explanation:
In biology, when a plant, such as a tree, is described as 'woody', it means that the plant has the ability to undergo secondary growth, which allows the stem to increase in thickness or girth. This secondary growth is accompanied by the addition of secondary vascular tissue and a cork layer, resulting in the formation of bark.
Woody plants, especially trees, may also exhibit the formation of annual rings as growth slows at the end of each season. These rings can be used to estimate the age of a tree.