deep understanding or knowledge of a subject
Wisdom is knowing things that help a person to live sensibly and make good decisions. Wisdom is defined differently by many cultures. Some say that wisdom is something a person learns as they grow older. Other cultures expect people to complete certain rituals in order to get wisdom.
If someone has wisdom, they are called wise. Most cultures from the past have had special people who were supposed to be wise. People asked them for advice when they had problems because they knew things that ordinary people did not know or could not know. They were often called "sages".
There are many stories in Western culture in which the owl is supposed to be a wise bird.