a tax, tariff or duty etc. that is imposed. Unlike taxes, tariffs, or duties, the primary purpose of an impost is to dissuade countries from discriminating against the imports or shipping of other nations. If the trade is non-discriminatory, then no impost is generally levied. It is therefore not intended as a revenue source, but rather as a way to regulate commerce
{i} one who pretends to be something he is not in order to deceive others, impersonator, pretender (also impostor); person who determines the rate of customs duty on imports