1) A) Unwritten law; B) levies on imported or exported goods.
(Sayles, George O. The King's Parliament of England, 144)
2) Used in three senses: A) the customary rules and procedures of a town, especially in legal matters; B) "the king's customs", i.e. the early medieval customary dues, like landgable and tolls, owed to the king; C) customs duties on the import or export of mechandise, including both local customs imposed in a particular port for its own profit and the national customs imposed (in England between 1203-6 and from 1275).
(Reynolds, Susan. An Introduction to the History of English Medieval Towns, 198)

Medieval glossary. 2014.