The Collaborative International Dictionary of English v.0.48:

Demurrer \De*mur"rer\, n.
   1. One who demurs.
      [1913 Webster]

   2. (Law) A stop or pause by a party to an action, for the
      judgment of the court on the question, whether, assuming
      the truth of the matter alleged by the opposite party, it
      is sufficient in law to sustain the action or defense, and
      hence whether the party resting is bound to answer or
      proceed further.
      [1913 Webster]

   Demurrer to evidence, an exception taken by a party to the
      evidence offered by the opposite party, and an objecting
      to proceed further, on the allegation that such evidence
      is not sufficient in law to maintain the issue, and a
      reference to the court to determine the point. --Bouvier.
      [1913 Webster]

WordNet (r) 3.0 (2006):

demurrer
    n 1: (law) a formal objection to an opponent's pleadings [syn:
         demur, demurral, demurrer]
    2: (law) any pleading that attacks the legal sufficiency of the
       opponent's pleadings
    3: a defendant's answer or plea denying the truth of the charges
       against him; "he gave evidence for the defense" [syn:
       defense, defence, denial, demurrer] [ant: criminal
       prosecution, prosecution]

Moby Thesaurus II by Grady Ward, 1.0:

65 Moby Thesaurus words for "demurrer":
   answer, apostate, argument, beef, bitch, boycott, challenge,
   complaint, compunction, counterstatement, defense, demonstration,
   demur, demurral, denial, difficulty, dissenter, dissentient,
   dissident, exception, expostulation, grievance,
   grievance committee, howl, indignation meeting, kick, march,
   nonconformist, nonviolent protest, objection, objector, opinionist,
   opposition voice, picketing, plea, pleading, pleadings, protest,
   protest demonstration, protestant, protestation, protester, qualm,
   question, rally, rebuttal, recusant, refutation, remonstrance,
   remonstration, reply, response, riposte, schismatic, scruple,
   sectarian, sectary, separatist, sit-in, special demurrer,
   special pleading, squawk, statement of defense, strike, teach-in



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

DEMURRER. (From the Latin demorari, or old French demorrer, to wait or
stay.) In pleading, imports, according to its etymology, that the objecting
party will not proceed with the pleading, because no sufficient statement
has been made on the other side; but will wait the judgment of the court
whether he is bound to answer. 5 Mod. 232; Co. Litt. 71, b; Steph. Pl. 61.
     2. A demurrer may be for insufficiency either in substance or in form
that is, it may be either on the ground that the case shown by the opposite
party is essentially insufficient, or on the ground that it is stated in an
artificial manner; for the law requires in every pleading, two thing's;
the one, that it be in matter sufficient; the other, that it be deduced and
expressed according to the forms of law; and if either the one or the other
of these be wanting, it is cause of demurrer. Hob. 164. A demurrer, as in
its nature, so also in its form, is of two kinds; it is either general or
special.
     3. With respect to the effect of a demurrer, it is, first, a rule, that
a demurrer admits all such matters of fact as are sufficiently pleaded. Bac.
Abr. Pleas, N 3; Com. Dig. Pleader, Q 5. Again, it is it rule that, on a
demurrer, the court will consider the whole record, and give judgment for
the party who, on the whole, appears to be entitled to it. Com. Dig.
Pleader, M. 1, M 2; Bad. Abr. Pleas. N 3; 5 Rep. 29 a: Hob. 56; 2 Wils. 150;
4 East, 502 1 Saund. 285 n. 5. For example, on a demurrer to the
replication, if the court think the replication bad, but perceive a
substantial fault in the plea, they will give judgment, not for the
defendant, but for the plaintiff; 2 Wils. R. 1&0; provided the declaration
be good; but if the declaration also be bad in substance, then upon the same
principle, judgment would be given for the defendant. 5 Rep. 29 a. For when
judgment is to be given, whether the issue be in law or fact, and whether
the cause have proceeded to issue or not, the court is always to examine the
whole record, and adjudge for the plaintiff or defendant, according to the
legal right, as it may on the whole appear.
     4. It is, however, subject to, the following exceptions; first, if the
plaintiff demur to a plea in abatement, and the court decide against the
plea, they will give judgment of respondeat ouster, without regard to any
defect in the declaration. Lutw. 1592, 1667; 1 Salk. 212; Carth. 172
Secondly, the court will not look back into the record, to adjudge in favor
of an apparent right in the plaintiff, unless the plaintiff have himself put
his action upon that ground. 5 Barn. & Ald 507. Lastly, the court, in
examining the whole record, to adjudge according to the apparent right, will
consider the right in matter of substance, and not in respect of mere form,
such as should have been the subject of a special demurrer. 2 Vent. 198-222.
     5. There can be no demurrer to a demurrer: for a demurrer upon a
demurrer, or pleading over when an issue in fact is offered, is a
discontinuance. Salk. 219; Bac. Abr. Pleas, N 2.
     6. Demurrers are general and special, and demurrers to evidence, and to
interrogatories.
     7.-1. A general demurrer is one which excepts to the sufficiency of a
previous pleading in general terms, without showing specifically the nature
of the objection; and such demurrer is sufficient, when the objection is on
matter of substance. Steph. Pl. 159; 1 Chit. Pl. 639; Lawes, Civ. Pl. 167;
Bac. Abr. Pleas, N 5; Co. Lit. 72 a.
     8.-2. A special demurrer is one which excepts to the sufficiency of
the pleadings on the,opposite side, and shows specifically the nature of the
objection and the particular ground of exception. Co. Litt. 72, a.; Bac.
Abr. Pleas, N 5.
     9. A special demurrer is necessary, where it turns on matter of form
only; that is, where, notwithstanding such objections, enough appears to
entitle the opposite party to judgment, as far as relates to the merits of
the cause. For, by two statutes, 27 Eliz. ch. 5, and 4 Ann. ch. 16, passed
with a view to the discouragement of merely formal objections, it is
provided in nearly the same terms, that the judges "shall give judgment
according to the very right of the cause and matter in law as it shall
appear unto them, without regarding any imperfection, omission, defect or
want of form, except those only 'Which the party demurring shall,
specifically. and particularly set down and express, together with his
demurrer, as the causes of the same." Since these statutes, therefore, no
mere matter of form can be objected to on a general demurrer; but the
demurrer must be in the special form, and the objection specifically stated.
But, on the other hand, it is to be observed, that, under a special
demurrer, the party may, on the argument, not only take advantage of the
particular faults which his demurrer specifies, but also of all objections
in substance, or regarding the very right of the cause, (as the statute
expresses it.) as under those statutes, need not be particularly set down.
It follows, therefore, that unless the objection be clearly of the
substantial kind, it is the safer course, in all cases, to demur specially.
Yet, where a general demurrer is plainly efficient, it is more usually
adopted in practice; because the effect of the special form being to apprise
the opposite party more distinctly of the nature of the objection, it is
attended with the inconvenience, of enabling him to prepare to maintain his
pleading by argument, or of leading him to apply the earlier to amend. With
respect to the degree of particularity, with which, under these statutes,
the special demurrer must assign the ground of objection, it may be
observed, that it is not sufficient to object, in general terms, that the
pleading is "uncertain, defective, and informal," or the like, but if is
necessarily to show in what, it respect, uncertain, defective, and informal.
1 Saund. 161, n. 1, 337 b, n. 3; Steph. Pl. 159, 161; 1 Chit. Pl. 642.
    10.- 3. A demurrer to evidence is analogous to a demurrer in pleading;
the party from whom it comes declaring that he will not proceed, because the
evidence offered on the other side, is not sufficient to maintain the issue.
Upon joinder in demurrer, by the opposite party, the jury are, in general,
discharged from giving any verdict; 1 Arch. Pr. 186; and the demurrer being
entered on record, is afterwards argued and decided by the court in banc;
and the judgment there given upon it, may ultimately be brought before a
court of error. See 2 H. Bl. 187 4 Chit. Pr. 15 Gould on Pl. c. 9, part 2,
Sec. 47 United States Dig. Pleading, Viii.
    11.-4. Demurrer to interrogatories. By this phrase is understood the
reasons which a witness tenders for not answering a particular question in
interrogatories. 2 Swanst. R. 194. Strictly speaking, this is not a
demurrer, which admits the facts stated, for the purpose of taking the.
opinion of the court but by an abuse of the term, the witness objection to
answer is called a demurrer, in the popular sense. Gresl. Eq. Ev. 61.
    12. The court are judicially to determine their validity. The witness
must state his objection very carefully, for these demurrers are held to
strict rules, and are readily overruled if they cover too much. 2 Atk. 524;
1 Y. & J. 32. See, in general, as to demurrers,, Bac. Abr. Pleas, N; Com.
Dig. Pleader, Q; Saund. Rep. Index, tit. Demurrers; Lawes Civ. Pl. ch. 8; 1
Chit. Pl. 639-649 Bouv. Inst. Index, h.t.