A person who advocates reciprocal conditions in trade; specifically (a) British, Politics a person who believes in the use of tariffs to secure mutually beneficial conditions in trade; a protectionist (now historical); (b) North American an opponent of tariffs; a proponent or supporter of free trade.
Of, relating to, or characteristic of reciprocitarians, or of the theory of reciprocity in trade.
Mid 19th century; earliest use found in The Economist. From reciprocity + -arian, after e.g. Trinitarian, Trinitarian, Unitarian, Unitarian.