What is Borough English?

Legal Definition
English law. This, as the name imports, relates exclusively to the English law.

2. It is a custom, in many ancient boroughs, by which the youngest son succeeds to the burgage tenement on the death of the father. 2 Bl. Com. 83.

3. In some parts of France, there was a custom by which the youngest son was entitled to an advantage over the other children in the estate of their father. iller. Rep. mot Mainete.
-- Bouviers Law Dictionary
Legal Definition
A custom prevalent in some parts of England, by which the youngest son iuberits the estate in preference to bis older brothers. 1 Bl. Comm. 75.
-- Black's Law Dictionary
Legal Definition
A descent to the youngest son.
-- Ballentine's Law Dictionary