The Collaborative International Dictionary of English v.0.48:

amnesty \am"nes*ty\ ([a^]m"n[e^]s*t[y^]), n. [L. amnestia, Gr.
   'amnhsti`a, a forgetting, fr. 'a`mnhstos forgotten,
   forgetful; 'a priv. + mna^sqai to remember: cf. F. amnistie,
   earlier amnestie. See Mean, v.]
   1. Forgetfulness; cessation of remembrance of wrong;
      oblivion.
      [1913 Webster]

   2. An act of the sovereign power granting oblivion, or a
      general pardon, for a past offense, as to subjects
      concerned in an insurrection.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Amnesty \Am"nes*ty\, v. t. [imp. & p. p. Amnestied; p. pr. &
   vb. n. Amnestying.]
   To grant amnesty to.
   [1913 Webster]

WordNet (r) 3.0 (2006):

amnesty
    n 1: a period during which offenders are exempt from punishment
    2: a warrant granting release from punishment for an offense
       [syn: pardon, amnesty]
    3: the formal act of liberating someone [syn: amnesty,
       pardon, free pardon]
    v 1: grant a pardon to (a group of people)

Moby Thesaurus II by Grady Ward, 1.0:

20 Moby Thesaurus words for "amnesty":
   absolution, exculpation, excuse, exemption, exoneration, grace,
   immunity, impunity, indemnity, nolle prosequi, non prosequitur,
   nonprosecution, pardon, redemption, remission, remission of sin,
   reprieve, shrift, sparing, stay



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

AMNESTY, government. An act of oblivion of past offences, granted by the
government to those who have been guilty of any neglect or crime, usually
upon condition that they return to their duty within a certain period.
     2. An amnesty is either express or implied; it is express, when so
declared in direct terms; and it is implied, when a treaty of peace is made
between contending parties. Vide Vattel, liv. 4, c. 2, Sec. 20, 21, 22;
Encycl. Amer. h.t.
     3. Amnesty and pardon, are very different. The former is an act of the
sovereign power, the object of which is to efface and to cause to be
forgotten, a crime or misdemeanor; the latter, is an act of the same
authority, which exempts the individual on whom it is bestowed from the
punishment the law inflicts for the crime he has committed. 7 Pet. 160.
Amnesty is the abolition and forgetfulness of the offence; pardon is
forgiveness. A pardon is given to one who is certainly guilty, or has been
convicted; amnesty, to those who may have been so.
     4. Their effects are also different. That of pardon, is the remission
of the whole or a part of the punishment awarded by the law; the conviction
remaining unaffected when only a partial pardon is granted: an amnesty on
the contrary, has the effect of destroying the criminal act, so that it is
as if it had not been committed, as far as the public interests are
concerned.
     5. Their application also differs. Pardon is always given to
individuals, and properly only after judgment or conviction: amnesty may be
granted either before judgment or afterwards, and it is in general given to
whole classes of criminals or supposed criminals, for the purpose of
restoring tranquillity in the state. But sometimes amnesties are limited,
and certain classes are excluded from their operation.



The Devil's Dictionary (1881-1906):

AMNESTY, n.  The state's magnanimity to those offenders whom it would
be too expensive to punish.