The Collaborative International Dictionary of English v.0.48:

Indorsement \In*dorse"ment\, n. [From Indorse; cf.
   Endorsement.] [Written also endorsement.]
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   1. The act of writing on the back of a note, bill, or other
      written instrument.
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   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.
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   3. Sanction, support, or approval; as, the indorsement of a
      rumor, an opinion, a course, conduct.
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   Blank indorsement. See under Blank. Indorser

The Collaborative International Dictionary of English v.0.48:

Blank \Blank\, a. [OE. blank, blonc, blaunc, blaunche, fr. F.
   blanc, fem. blanche, fr. OHG. blanch shining, bright, white,
   G. blank; akin to E. blink, cf. also AS. blanc white. ?98.
   See Blink, and cf. 1st Blanch.]
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   1. Of a white or pale color; without color.
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            To the blank moon
            Her office they prescribed.           --Milton.
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   2. Free from writing, printing, or marks; having an empty
      space to be filled in with some special writing; -- said
      of checks, official documents, etc.; as, blank paper; a
      blank check; a blank ballot.
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   3. Utterly confounded or discomfited.
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            Adam . . . astonied stood, and blank. --Milton.
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   4. Empty; void; without result; fruitless; as, a blank space;
      a blank day.
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   5. Lacking characteristics which give variety; as, a blank
      desert; a blank wall; destitute of interests, affections,
      hopes, etc.; as, to live a blank existence; destitute of
      sensations; as, blank unconsciousness.
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   6. Lacking animation and intelligence, or their associated
      characteristics, as expression of face, look, etc.;
      expressionless; vacant. "Blank and horror-stricken faces."
      --C. Kingsley.
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            The blank . . . glance of a half returned
            consciousness.                        --G. Eliot.
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   7. Absolute; downright; unmixed; as, blank terror.
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   Blank bar (Law), a plea put in to oblige the plaintiff in
      an action of trespass to assign the certain place where
      the trespass was committed; -- called also common bar.


   Blank cartridge, a cartridge containing no ball.

   Blank deed. See Deed.

   Blank door, or Blank window (Arch.), a depression in a
      wall of the size of a door or window, either for
      symmetrical effect, or for the more convenient insertion
      of a door or window at a future time, should it be needed.


   Blank indorsement (Law), an indorsement which omits the
      name of the person in whose favor it is made; it is
      usually made by simply writing the name of the indorser on
      the back of the bill.

   Blank line (Print.), a vacant space of the breadth of a
      line, on a printed page; a line of quadrats.

   Blank tire (Mech.), a tire without a flange.

   Blank tooling. See Blind tooling, under Blind.

   Blank verse. See under Verse.

   Blank wall, a wall in which there is no opening; a dead
      wall.
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Bouvier's Law Dictionary, Revised 6th Ed (1856):

BLANK INDORSEMENT, contracts. An indorsement which does not mention the name
of the person in whose favor it is made; it is usually made by writing the
name of the indorser on the back of the bill. Chit. Bills, 170.
     2. When a bill or note has been indorsed in blank, its negotiability
cannot afterwards be restrained. 1 Esp. N. P. Cas. 180; 1 Bl. Rep. 295. As
many persons as agree may join in suing on a bill when indorsed in blank;
for although it was given to one alone, yet by allowing the others to join
in the suit, he has 'Made them sharers in his rights. 8 Camp. N. P. Cas.
239. Vide Indorsement; Negotiable paper; Restrictive indorsement.