The Collaborative International Dictionary of English v.0.48:

Forgery \For"ger*y\, n.; pl. Forgeries. [Cf. F. forgerie.]
   1. The act of forging metal into shape. [Obs.]
      [1913 Webster]

            Useless the forgery
            Of brazen shield and spear.           --Milton.
      [1913 Webster]

   2. The act of forging, fabricating, or producing falsely;
      esp., the crime of fraudulently making or altering a
      writing or signature purporting to be made by another; the
      false making or material alteration of or addition to a
      written instrument for the purpose of deceit and fraud;
      as, the forgery of a bond. --Bouvier.
      [1913 Webster]

   3. That which is forged, fabricated, falsely devised, or
      counterfeited.
      [1913 Webster]

            These are the forgeries of jealously. --Shak.
      [1913 Webster]

            The writings going under the name of Aristobulus
            were a forgery of the second century. --Waterland.

   Syn: Counterfeit; Forgery.

   Usage: Counterfeit is chiefly used of imitations of coin, or
          of paper money, or of securities depending upon
          pictorial devices and engraved designs for identity or
          assurance of genuineness. Forgery is more properly
          applied to making a false imitation of an instrument
          depending on signatures to show genuineness and
          validity. --Abbott.
          [1913 Webster]

WordNet (r) 3.0 (2006):

forgery
    n 1: a copy that is represented as the original [syn:
         counterfeit, forgery]
    2: criminal falsification by making or altering an instrument
       with intent to defraud

Moby Thesaurus II by Grady Ward, 1.0:

86 Moby Thesaurus words for "forgery":
   bad check, bad money, base coin, bogus money, canard,
   certified copy, cheat, clinquant, coinage, coining, concoction,
   copy, copying, counterfeit, counterfeit money, counterfeiting,
   dummy, ectype, emulation, extravaganza, fable, fabrication,
   fair copy, faithful copy, fake, fakement, fakery, false money,
   falsification, fiction, figment, following, frame-up, fraud,
   fraudulence, green goods, hit-off, hoax, icon, image, imitation,
   impersonation, impostor, imposture, impression, invention, junk,
   kite, likeness, mimesis, mintage, mirroring, mock, myth,
   onomatopoeia, parody, paste, pasticcio, pastiche, phony, picture,
   pinchbeck, plagiarism, plagiary, portrait, put-on, put-up job,
   queer, repetition, representation, resemblance, rip-off, romance,
   rubber check, semblance, sham, shoddy, similitude, simulacrum,
   simulation, stamping, striking, swindle, takeoff, tinsel,
   whited sepulcher



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

FORGERY, crim. law. Forgery at common law has been held to be "the
fraudulent making and alteration of a writing to the prejudice of another
man's right." 4 Bl. Com. 247. By a more modern writer, it is defined, as "a
false making; a making malo animo, of any written instrument, for the
purpose of fraud and deceit." 2 East, P. C. 852.
     2. This offence at common law is of the degree of a misdemeanor. 2
Russell, 1437. There are many kinds of forgery, especially subjected to
punishment by statutes enacted by the national and state legislatures.
     3. The subject will be considered, with reference, 1. To the making or
alteration requisite to constitute forgery. 2. The written instruments in
respect of which forgery may be committed. 3. The fraud and deceit to the
prejudice of another man's right. 4. The statutory provisions under the laws
of the United States, on the subject of forgery.
     4. - 1. The making of a whole written instrument in the name of another
with a fraudulent intent is undoubtedly a sufficient making but a fraudulent
insertion, alteration, or erasure, even of a letter, in any material part of
the instrument, whereby a new operation is given to it, will amount to a
forgery; and this, although it be afterwards executed by a person ignorant
of the deceit. 2 East, P. C. 855.
     5. The fraudulent application of a true signature to a false instrument
for which it was not intended, or vice versa, will also be a forgery. For
example, it is forgery in an individual who is requested to draw a will for
a sick person in a particular way, instead of doing so, to insert legacies
of his own head, and then procuring the signature of such sick person to be
affixed to the paper without revealing to him the legacies thus fraudulently
inserted. Noy, 101; Moor, 759, 760; 3 Inst. 170; 1 Hawk. c. 70, s. 2; 2
Russ. on Cr. 318; Bac. Ab. h.t. A.
     6. It has even been intimated by Lord Ellenborough, that a party who
makes a copy of a receipt, and adds to such copy material words not in the
original, and then offers it in evidence on the ground that the original has
been lost, may be prosecuted for forgery. 5 Esp. R. 100.
     7. It is a sufficient making where, in the writing, the party assumes
the name and character of a person in existence. 2 Russ. 327. But the
adoption of a false description and addition, where a false name is not
assumed, and there is no person answering the description, is not a forgery.
Russ. & Ry. 405.
     8. Making an instrument in a fictitious name, or the name of a non-
existing person, is equally a forgery, as making it in the name of au
existing person; 2 East, P. C. 957; 2 Russ. on Cr. 328; and although a man
may make the instrument in his own name, if he represent it as the
instrument of another of the same name, when in fact there is no such
person, it will be a forgery in the name of a non-existing person.; 2 Leach,
775; 2 East, P. C. 963; but the correctness of this decision has been
doubted. Rosc. Cr. Ev. 384.
     9. Though, in general, a party cannot be guilty of forgery by a mere
non-feasance, yet, if in drawing a will, he should fraudulently omit a
legacy, which he had been directed to insert, and by the omission of such
bequest, it would cause a material alteration in the limitation of a bequest
to another; as, where the omission of a devise of an estate for life to one,
causes a devise of the same lands to another to pass a present estate which
would otherwise have passed a remainder only, it would be a forgery. Moor,
760; Noy, 101; 1 Hawk. c. 70, s. 6; 2 East, P. C. 856; 2 Russ. on Cr. 320.
    10. It may be observed, that the offence of forgery may be complete
without a publication of the forged instrument. 2 East, P. C. 855; 3 Chit.
Cr. L. 1038.
    11. - 2. With regard to the thing forged, it may be observed, that it
has been holden to be forgery at common law fraudulently to falsify, or
falsely make records and other matters of a public nature; 1 Rolle's Ab. 65,
68; a parish register; 1 Hawk. c. 70; a letter in the name of a magistrate,
the governor of a gaol, directing the discharge of prisoner. 6 Car. & P.
129; S. C. 25 Eng. C. L. R. 3 1 5.
    12. With regard to private writings, it is forgery fraudulently to
falsify or falsely to make a deed or will; 1 Hawk. b. 1, c. 70, s. 10 or any
private document, whereby another person may be prejudiced. Greenl. Rep.
365; Addis. R. 33; 2 Binn. R. 322; 2 Russ. on Or. b. 4, c. 32, s. 2;  2
East, P. C. 861; 3 Chit. Cr. Law, 1022 to 1038.
    13. - 3. The intent must be to defraud another, but it is not requisite
that any one should have been injured it is sufficient that the instrument
forged might have proved prejudicial. 3 Gill & John. 220; 4 W. C. C. R. 726.
It has been holden that the jury ought to infer an intent to defraud the
person who would have to pay the instrument, if it were genuine, although
from the manner of executing the forgery, or from the person's ordinary
caution, it would not be likely to impose upon him; and although the object
was general to defraud whoever might take the instrument, and the intention
of the defrauding in particular, the person who would have to pay the
instrument, if genuine, did not enter into the contemplation of the
prisoner. Russ. & Ry. 291; vide Russ.. on Cr. b. 4, c. 32, s. 3; 2 East, P.
C. 853; 1 Leach, 367; 2 Leach, 775; Rosc. Cr. Ev. 400.
    14.- 4. Most, and perhaps all the states in the Union, have passed laws
making certain acts to be forgery, and the national legislature has also
enacted several on this subject, which are here referred to. Act of March 2,
1803, 2 Story's L. U. S. 888; Act of March 3, 1813, 2 Story's L. U. S. 1304
Act of March 1, 1823, 3 Story's L. U. S. 1889; Act of March 3, 1825, 3
Story's L. U. S. 2003; Act of October 12, 1837, 9 Laws U. S. 696.
    15. The term forgery, is also applied to the making of false or
counterfeit coin. 2 Virg. Cas. 356. See 10 Pet. 613; 4 Wash. C. C. 733. For
the law respecting the forgery of coin, see article Money. And for the act
of congress punishing forgery in the District of Columbia, see 4 Sharsw.
Cont, of Story's Laws U. S. 2234. Vide, generally, Hawk. b. 1, c. 51 and 70;
3 Chit. Cr. Law, 1022 to 1048; 4 Bl. Com. 247 to 250; 2 East, P. C. 840 to
1003; 2 Russ. on Cr. b. 4, c. 32; 13 Vin. Ab. 459; Com. Dig. h.t.; Dane's
Ab. h.t. Williams' Just. h.t. Burn's Just. h.t.; Rose. Cr. Ev. h.t.;
Stark. Ev. h.t. Vide article Frank.