n. 1 a the usual way of behaving or acting (a slave to custom). b a particular established way of behaving (our customs seem strange to foreigners). 2 Law established usage having the force of law. 3 business patronage; regular dealings or customers (lost a lot of custom). 4 (in pl.; also treated as sing.) a a duty levied on certain imported and exported goods. b the official department that administers this. c the area at a port, frontier, etc., where customs officials deal with incoming goods, baggage, etc. custom-built (or -made etc.) made to a customer's order. custom-house the office at a port or frontier etc. at which customs duties are levied. customs union a group of States with an agreed common tariff, and usu. free trade with each other.
[ ME and OF custume ult. f. L consuetudo -dinis: see CONSUETUDE ]