The Collaborative International Dictionary of English v.0.48:

Hypothecation \Hy*poth`e*ca"tion\, n. [LL. hypothecatio.]
   1. (Civ. Law) The act or contract by which property is
      hypothecated; a right which a creditor has in or to the
      property of his debtor, in virtue of which he may cause it
      to be sold and the price appropriated in payment of his
      debt. This is a right in the thing, or jus in re.
      --Pothier. B. R. Curtis.
      [1913 Webster]

            There are but few cases, if any, in our law, where
            an hypothecation, in the strict sense of the Roman
            law, exists; that is a pledge without possession by
            the pledgee.                          --Story.
      [1913 Webster]

   Note: In the modern civil law, this contract has no
         application to movable property, not even to ships, to
         which and their cargoes it is most frequently applied
         in England and America. See Hypothecate. --B. R.
         Curtis. Domat.
         [1913 Webster]

   2. (Law of Shipping) A contract whereby, in consideration of
      money advanced for the necessities of the ship, the
      vessel, freight, or cargo is made liable for its
      repayment, provided the ship arrives in safety. It is
      usually effected by a bottomry bond. See Bottomry.
      [1913 Webster]

   Note: This term is often applied to mortgages of ships.
         [1913 Webster]

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

HYPOTHECATION, civil law. This term is used principally in the civil law; it
is defined to be a right which a creditor has over a thing belonging to
another, and which consists in the power to cause it to be sold, in order to
be paid his claim out of the proceeds.
     2. There are two species of hypothecation, one called pledge, pignus,
and, the other properly denominated hypothecation. Pledge is that species,
of hypothecation which is contracted by the delivery of the debtor to the
creditor, of the thing hypothecated. Hypothecation, properly so called, is
that which is contracted without delivery of the thing hypothecated. 2
Bell's Com. 25, 5th ed.
     3. Hypothecation is further divided into general and special when the
debtor hypothecates to his creditor all his estate and property, which he
has, or may have, the hypothecation is general; when the hypothecation is
confined to a particular estate, it is special.
     4. Hypothecations are also distinguished into conventional, legal, and
tacit. 1. Conventional hypothecations are those which arise by the agreement
of the parties. Dig. 20, 1, 5.
     5.-2. Legal hypothecation is that which has not been agreed upon by
any contract, express or implied; such as arises from the effect of
judgments and executions.
     6.-3. A tacit, which is also a legal hypothecation, is that which the
law gives in certain cases, without the consent of the parties, to secure
the creditor; such as, 1st. The lien which the public treasury has over the
property of public debtors. Code, 8, 15, 1. 2d. The landlord has a lien on
the goods in the house leased, for the payment of his rent. Dig. 20, 2, 2;
Code, 8, 15, 7, 3d. The builder has a lien, for his bill, on the house he
has built. Dig. 20, 1. 4th, The pupil has a lien on the property of the
guardian for the balance of his account. Dig. 46, 6, 22; Code, 6, 37, 20.
5th. There is hypothecation of the goods of a testator for the security of a
legacy he has given. Code, 6, 43, 1.
     7. In the common law, cases of hypothecation, in the strict sense of
the civil law, that is, of a pledge of a chattel, without possession by the
pledgee, are scarcely to be found; cases of bottomry bonds and claims for
seamen's wages, against ships are the nearest approach to it; but these are
liens and privileges rather than hypothecations. Story, Bailm. Sec. 288. It
seems that chattels not in existence, though they cannot be pledged, can be
hypothecated, so that the lien will attach, as soon as the chattel has been
produced. 14 Pick. R. 497.
     Vide, generally, Poth. de l'Hypoth‚que; Poth. Mar. Contr. translated by
Cushing, note. 26, p. 145; Commercial Code of France, translated by Rodman,
note 52, p. 351; Merl. R‚pertoire, mot Hypoth‚que, where the subject is
fully considered; 2 Bro. Civ. Law, 195; Ayl. Pand. 524; 1 Law Tracts, 224;
Dane's Ab. h.t.; Abbott on Ship. Index, h.t.; 13 Ves. 599; Bac. Ab.
Merchant, &c. G; Civil Code of Louis. tit. 22, where this sort of security
bears the name of mortgage. (q.v.)