A more thorough explanation:

Definition: Defensum (di-fen-səm), n. [Law Latin “an inclosure”]

Historical:

1. A portion of an open field allotted for corn or hay but not for feeding.
2. A wood partially enclosed to prevent the cattle from damaging the undergrowth.
3. A prohibition.

Explanation:

Defensum is a Latin term that has three historical meanings. The first meaning refers to a portion of an open field that is used for growing crops such as corn or hay, but not for feeding animals. The second meaning refers to a wood that is partially enclosed to prevent cattle from damaging the undergrowth. The third meaning refers to a prohibition, which is a rule or law that forbids something from happening.

Examples:

• A farmer has a defensum in his open field where he grows corn and hay, but he does not allow his animals to graze there.
• A forest ranger creates a defensum by putting up a fence around a section of the woods to protect the young trees from being eaten by cattle.
• A city council passes a defensum that prohibits smoking in public parks to protect the health of non-smokers.

The examples illustrate the different historical meanings of defensum. In the first example, the defensum is a portion of an open field that is used for growing crops but not for feeding animals. In the second example, the defensum is a wood that is partially enclosed to protect the undergrowth from being damaged by cattle. In the third example, the defensum is a prohibition that forbids smoking in public parks to protect the health of non-smokers.