The Collaborative International Dictionary of English v.0.48:

Abrogation \Ab`ro*ga"tion\, n. [L. abrogatio, fr. abrogare: cf.
   F. abrogation.]
   The act of abrogating; repeal by authority.    --Hume.
   [1913 Webster]

WordNet (r) 3.0 (2006):

abrogation
    n 1: the act of abrogating; an official or legal cancellation
         [syn: abrogation, repeal, annulment]

Moby Thesaurus II by Grady Ward, 1.0:

58 Moby Thesaurus words for "abrogation":
   abjuration, abjurement, abolishment, abolition,
   absolute contradiction, annulment, cancel, canceling, cancellation,
   cassation, contradiction, contrary assertion, contravention,
   controversion, countering, countermand, counterorder, crossing,
   defeasance, denial, disaffirmation, disallowance, disavowal,
   disclaimer, disclamation, disownment, disproof, forswearing,
   gainsaying, impugnment, invalidation, nullification, recall,
   recantation, refutation, renege, renunciation, repeal, repudiation,
   rescinding, rescindment, rescission, retractation, retraction,
   reversal, revocation, revoke, revokement, setting aside,
   suspension, vacation, vacatur, voidance, voiding, waiver, waiving,
   withdrawal, write-off



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

ABROGATION, in the civil law, legislation. The destruction or annulling of a
former law, by an act of the legislative power, or by usage.  A law may be
abrogated or only derogated from; it is abrogated when it is totally
annulled; it is derogated from when only a part is abrogated: derogatur
legi, cum pars detrahitur; abrogatur legi, cum prorsus tollitur. Dig lib..
50, t. 17, 1, 102. Lex rogatur dum fertur; abrogatur dum tollitur; derogatur
eidem dum quoddam ejus caput aboletuer; subrogatur dum aliquid ei adjicitur;
abrogatur denique, quoties aliquid in ea mutatur. Dupin, Proleg. Juris, Art.
iv.
     2. Abrogation is express or implied; it is express when it, is
literally pronounced by the new law, either in general terms, as when a
final clause abrogates or repeals all laws contrary to the provisions of the
new one, or in particular terms, as when it abrogates certain preceding laws
which are named.
     3. Abrogation is implied when the new law contains provisions which are
positively, contrary to the former laws, without expressly abrogating such
laws: for it is a posteriora derogant prioribus. 3 N. S. 190; 10 M. R. 172.
560.  It is also implied when the order of things for which the law had been
made no longer exists, and hence the motives which had caused its enactment
have ceased to operate; ratione legis omnino cessante cessat lex. Toullier,
Droit Civil Francais, tit. prel. Sec. 11, n. 151. Merlin, mot Abrogation.