The Collaborative International Dictionary of English v.0.48:

Surplusage \Sur"plus*age\, n. [See Surplus, and cf.
   Superplusage.]
   1. Surplus; excess; overplus; as, surplusage of grain or
      goods beyond what is wanted.
      [1913 Webster]

            Take what thou please of all this surplusage.
                                                  --Spenser.
      [1913 Webster]

            A surplusage given to one part is paid out of a
            reduction from another part of the same creature.
                                                  --Emerson.
      [1913 Webster]

   2. (Law) Matter in pleading which is not necessary or
      relevant to the case, and which may be rejected.
      [1913 Webster]

   3. (Accounts) A greater disbursement than the charge of the
      accountant amounts to. [Obs.] --Rees.
      [1913 Webster]

WordNet (r) 3.0 (2006):

surplusage
    n 1: a quantity much larger than is needed [syn: excess,
         surplus, surplusage, nimiety]

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

SURPLUSAGE, pleading. A superfluous and useless statement of matter wholly
foreign and impertinent to the cause.
     2. In general surplusagium non nocet, according to the maxim utile per
inutile non vitiatur; therefore if a man in his declaration, plea, &c., make
mention of a thing which need, not be stated, but the matter set forth is
grammatically right, and perfectly sensible, no advantage can be taken on
demurrer. Com. Dig. Pleader, C 28, E 2; 1 Salk. 325; 4 East, 400; Gilb. C.
P. 131; Bac. Ab. Pleas, 1, 4; Co. Litt. 303, b; 2 Saund. 306, n. 14; 5 East
444; 1 Chit. Pl. 282; Lawes on Pl. 63; 7 John. 462; 3 Day, 472; 2 Mass. R.
283; 13 John. 80.
     3. When, by an unnecessary allegation the plaintiff shows he has no
cause of action, the defendant may demur. Com. Dig. Pleader, c. 29; Bac. Ab.
Pleas, 1, 4; see 2 East, 451; 4 East, 400; Dougl. 667; 2 Bl. Rep. 842; 3
Cranch, 193; 2 Dall. 300; 1 Wash. R. 257.
     4. When the surplusage is not grammatically set right, or it is
unintelligible and, no sense at all can be given it, or it be contradictory
or repugnant to what is before alleged, the adversary may take advantage of
it on special demurrer. Gilb. C. P. 132; Lewes on Pl. 64.
     5. When a party alleges a material matter with an unnecessary detail of
circumstances, and the essential and non-essential parts of a statement are,
in their nature, so connected as to be incapable of separation, the opposite
party may include under his traverse the whole matter alleged. And as it is
an established rule that the evidence must correspond with the allegations,
it follows that the party who has thus pleaded such unnecessarily matter
will be required to prove it, and thus he is required to sustain an
increased burden of proof, and incurs greater danger of failure at the
trial. For example, if in justifying the taking of cattle damage feasant, in
which case it is sufficient to allege that they were doing damage to his
freehold, he should state a seisin in fee, which is traversed, be must prove
a seisin in fee. Dyer, 365; 2 Saund. 206, a, note 22 Steph. on Pl. 261, 262;
1 Smith's Lead. Cas. 328, note; 1 Greenl. Ev. Sec. 51 1 Chit. Pl. 524, 525;
U. S. Dig. Pleading, VII. c.



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

SURPLUSAGE, accounts. A greater disbursement than the charges of the
accountant amount to.