impost

n. tax; weight carried by a horse in a race; column supporting an arch (Architecture)

Impost may mean:A type of extra taxA handicap (usually a lead weight) used in horse racingThe topmost part of an architectural column
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Noun
1. money collected under a tariff
(synonym) customs, customs duty, custom
(hypernym) duty, tariff
(hyponym) ship money
2. the lowest stone in an arch -- from which it springs
(synonym) springer
(hypernym) stone
(part-holonym) arch

n. impost, tax

(n.)
The top member of a pillar, pier, wall, etc., upon which the weight of an arch rests.
  

(n.)
That which is imposed or levied; a tax, tribute, or duty; especially, a duty or tax laid by goverment on goods imported into a country.