A forest in full leaf, as in summer.
"The children ran freely through the greenwood where sunlight filtered through the dense canopy of leaves."
In plain English: Greenwood is an old-fashioned word for green wood, meaning fresh branches and trees that haven't been cut down yet.
"The children played hide-and-seek in the greenwood during their summer break."
A surname.
"Many people in the village shared the greenwood family name after their ancestors settled there centuries ago."
The word comes from Middle English grene wode, which originally described a forest full of fresh leaves or unseasoned timber used for fires. It entered modern usage as the common term for any lush, wooded area where trees are still growing and have not yet been cut down.