The value (or in some cases small set of values) of a property associated with unassigned code points or with encoded characters for which the property is irrelevant.

• For example, for most Boolean properties, "false" is the default property value.

• Some properties, particularly enumerated properties, specify a particular, unique value as their default value. For example, "XX" is the default property value for the Line_Break property.
• A default property value is typically defined implicitly, to avoid having to repeat long lists of unassigned code points.
• In the case of some properties with arbitrary string values, the default property value is an implied null value. For example, the fact that there is no Unicode character name for unassigned code points is equivalent to saying that the default property value for the Name property for an unassigned code point is a null string.