The Collaborative International Dictionary of English v.0.48:

Indorsement \In*dorse"ment\, n. [From Indorse; cf.
   Endorsement.] [Written also endorsement.]
   [1913 Webster]
   1. The act of writing on the back of a note, bill, or other
      written instrument.
      [1913 Webster]

   2. That which is written on the back of a note, bill, or
      other paper, as a name, an order for, or a receipt of,
      payment, or the return of an officer, etc.; a writing,
      usually upon the back, but sometimes on the face, of a
      negotiable instrument, by which the property therein is
      assigned and transferred. --Story. Byles. Burrill.
      [1913 Webster]

   3. Sanction, support, or approval; as, the indorsement of a
      rumor, an opinion, a course, conduct.
      [1913 Webster]

   Blank indorsement. See under Blank. Indorser

WordNet (r) 3.0 (2006):

indorsement
    n 1: a promotional statement (as found on the dust jackets of
         books); "the author got all his friends to write blurbs for
         his book" [syn: endorsement, indorsement, blurb]
    2: a speech seconding a motion; "do I hear a second?" [syn:
       second, secondment, endorsement, indorsement]
    3: formal and explicit approval; "a Democrat usually gets the
       union's endorsement" [syn: sanction, countenance,
       endorsement, indorsement, warrant, imprimatur]
    4: a signature that validates something; "the cashier would not
       cash the check without an endorsement" [syn: endorsement,
       indorsement]
    5: the act of endorsing; "a star athlete can make a lot of money
       from endorsements" [syn: endorsement, indorsement]

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

INDORSEMENT, crim. law, practice. When a warrant for the arrest of a person
charged with a crime has been issued by a justice of the peace of one
county, which is to be executed in another county, it is necessary in some
states, as in Pennsylvania, that it should be indorsed by a justice of the
county where it is to be executed: this indorsement is called backing. (q.v.)




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

INDORSEMENT, contracts. In its most general acceptation, it is what is
written on the back of an instrument of writing, and which has relation to
it; as, for example, a receipt or acquittance on a bond; an assignment on a
promissory note.
     2. Writing one's name on the back of a bill of exchange, or a
promissory note payable to order, is what is usually called, an indorsement.
It will be convenient to consider, 1. The form of an indorsement; and, 2.
Its effect.
     3.-1. An indorsement is in full, or in blank. In full, when mention
is made of the name of the indorsee; and in blank, when the name of the
indorsee is not mentioned. Chitty on Bills, 170; 13 Serg. & Rawle, 315. A
blank indorsement is made by writing the name of the indorser on the back; a
writing or assignment on the face of the note or bill would, however, be
considered to have the force and effect of an indorsement. 16 East, R. 12.
when an indorsement has been made in blank any after attempt to restrain the
negotiability of the bill will be unavailing. 1 E.N. P. C. 180; 1 Bl. Rep.
295; Ham. on Parties 104.
     4. Indorsements may also be restrictive conditional, or qualified. A
restrictive indorsement may restrain the negotiability of a bill, by using
express words to that effect, as by indorsing it "payable to J. S. only," or
by using other words clearly demonstrating his intention to do so. Dougl.
637. The indorser may also make his indorsement conditional, and if the
condition be not performed, it will be invalid. 4 Taunt. Rep. 30. A
qualified indorsement is one which passes the property in the bill to the
indorsee, but is made without responsibility to the indorser; 7 Taunt. R.
160; the words commonly used are, sans recours, without recourse. Chit. on
Bills, 179; 3 Mass. 225; 12 Mass. 14, 15.
     5.-2. The effects of a regular indorsement may be considered, 1. As
between the indorser and the indorsee. 2. Between the indorser and the
acceptor. And, 3. Between the indorser and future parties to the bill.
     6.-1. An indorsement is sometimes an original engagement;as, when a
man draws a bill payable to his own order, and indorses it; mostly, however,
it operates as an assignment, as when the bill is perfect, and the payee
indorses it over to a third person. As an assignment, it carries with it all
the rights which the indorsee had, with a guaranty of the solvency of the
debtor. This guaranty is, nevertheless, upon condition that the holder will
use due diligence in making a demand of payment from the acceptor, and give
notice of non-acceptance or non-payment. 13 Serg. Rawle, 311.
     7.-2. As between the indorsee and the acceptor, the indorsement has
the effect of giving to the former all the rights which the indorser had
against the acceptor, and all other parties liable on the bill, and it is
unnecessary that the acceptor or other party should signify his consent or
knowledge of the indorsement; and if made before the bill is paid, it
conveys all these rights without any set-off, as between the antecedent
parties. Being thus fully invested with all the rights in the bill, the
indorsee may himself indorse it to another when he becomes responsible to
all future patties as an indorser, as the others were to him.
     8.-3. The indorser becomes responsible by that act to all persons who
may afterwards become party to the bill.
     Vide Chitty on Bills, ch. 4; 3 Kent, Com. 58; Vin. Abr. Indorsement;
Com. Dig. Fait, E 2; 13 Serg. & Rawle, 311; Merl. Repert. mot Endorsement
Pard. Droit Com. 344-357; 7 Verm. 356; 2 Dana, R. 90; 3 Dana, R. 407; 8
Wend. 600; 4 Verm. 11; 5 Harr. & John. 115; Bouv. Inst. Index, h.t.