Old wood
‘Old wood’ is usually used to describe stem growth which is more than one season old. This can be growth in terms of the lengthening of the stem (where the new wood is at the tip) or in terms of the widening of the stem (where the new wood forms around the circumference of the old wood).
The term is often used in pruning, in reference to the lengthening growth of stems. It’s important to understand what is old wood when pruning as some plants (particularly many conifers) will not grow from old wood.