The Collaborative International Dictionary of English v.0.48:

Importation \Im`por*ta"tion\, n. [Cf. F. importation. See
   Import, v. t.]
   1. The act of carrying, conveying, or delivering. [R.]
      [1913 Webster]

   2. The act or practice of importing, or bringing into a
      country or state; -- opposed to exportation.
      [1913 Webster]

   3. That which is imported; commodities or wares introduced
      into a country from abroad.
      [1913 Webster]

WordNet (r) 3.0 (2006):

importation
    n 1: the commercial activity of buying and bringing in goods
         from a foreign country [syn: importing, importation]
    2: commodities (goods or services) bought from a foreign country
       [syn: import, importation] [ant: export, exportation]

Bouvier's Law Dictionary, Revised 6th Ed (1856):

IMPORTATION, comm. law. The act of bringing goods and merchandise into the
United States from a foreign country. 9 Cranch, 104, 120; 5 Cranch, 368; 2
Mann. & Gr. 155, note a.
     2. To prevent the mischievous interference of the several states with
the national commerce, the constitution of the United States, art. 1, s. 10,
provides as follows: "No state shall, without the consent of the congress,
lay any imposts or duties on imports or exports, except what may be
absolutely necessary for executing its inspection laws, and the net produce
of all duties and imposts, laid by any state on imports or exports, shall be
for the use of the treasury of the United States; and all such laws shall be
subject to the revision and control of the congress."
     3. This apparently plain provision has received a judicial
construction. In the year 1821, the legislature of Maryland passed an act
requiring that all importers of foreign articles, commodities, &c., by the
bale or package, of wine, rum, &c., and other persons selling the same by
wholesale, bale or package, hogshead, barrel or tierce, should, before they
were authorized to sell, take out a license for which they were to pay fifty
dollars, under certain penalties. A question arose whether this act was or
was not a violation of the constitution of the United States, and
particularly of the above clause, and the supreme court decided against the
constitutionality of the law. 12 Wheat. 419.
     4. The act of congress of March 1, 1817, 3 Story, L. U. S. 1622,
provides:
     5.-1. That, after the 30th day of September next, no goods, wares, or
merchandise, shall be imported into the United States from any foreign port
or place, except in vessels of the United States, or in such foreign vessels
as truly or wholly belong to the citizens or subjects of that country of
which the goods are the growth, production or manufacture; or from which
such goods, wares or merchandise, can only be or most usually are, first
shipped for transportation: Provided, nevertheless, That this regulation
shall not extend to the vessels of any foreign nation which has not adopted,
and which shall not adopt a similar regulation.
     6.-2. That all goods, wares or merchandise, imported into the United
States contrary to the true intent and meaning of this act, and the ship or
vessel wherein the same shall be imported, together with her cargo, tackle,
apparel, and furniture, shall be forfeited to the United States and such
goods, wares, or merchandise, ship, or vessel, and cargo, shall be liable to
be seized, prosecuted, and condemned, in like manner, and under the same
regulations, restrictions, and provisions, as have been heretofore
established for the recovery, collection, distribution, and remission, of
forfeitures to the United States by the several revenue laws.
     7.-4. That no goods, wares, or merchandise, shall, be imported, under
penalty of forfeiture thereof, from one port of the United States to another
port of the United States, in a vessel belonging wholly or in part to a
subject of any foreign power; but this clause shall not be construed to
prohibit the sailing of any foreign vessel from one to another port of the
United States, provided no goods, wares, or mere other than those imported
in such vessel from some foreign port, and which shall not have been
unladen, shall be carried from one port or place to another in the United
States.
     8.-6. That after the 30th day of September next, there shall be paid
upon every ship or vessel of the United States, which shall be entered in
the United States from any foreign port or place, unless the officers, and
at least two-thirds of the crew thereof, shall be proved citizens of the
United States, or persons not the Subjects of any foreign prince or state,
to the satisfaction of the collector, fifty cents per ton: And provided
also, that this section shall not extend to ships or vessels of the United
States, which are now on foreign voyages, or which may depart from the
United States prior to the first day of May next, until after their return
to some port of the United States.
     9.- 7. That the several bounties and remissions, or abatements of duty,
allowed by this act, in the case of vessels having a certain proportion of
seamen who are American citizens, or persons not the subjects of any foreign
power, shall be allowed only, in the case of vessels having such proportion
of American seamen during their whole voyage, unless in case of sickness,
death or desertion, or where the whole or part of the crew shall have been
taken prisoners in the voyage. Vide article Entry of goods at the Custom-
house.