The Collaborative International Dictionary of English v.0.48:

Plural \Plu"ral\, n. (Gram.)
   The plural number; that form of a word which expresses or
   denotes more than one; a word in the plural form.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Plural \Plu"ral\, a. [L. pluralis, from plus, pluris, more; cf.
   F. pluriel, OF. plurel. See Plus.]
   Relating to, or containing, more than one; designating two or
   more; as, a plural word.
   [1913 Webster]

         Plural faith, which is too much by one.  --Shak.
   [1913 Webster]

   Plural number (Gram.), the number which designates more
      than one. See Number, n., 8.
      [1913 Webster]

WordNet (r) 3.0 (2006):

plural
    adj 1: composed of more than one member, set, or kind [ant:
           singular]
    2: grammatical number category referring to two or more items or
       units [ant: singular]
    n 1: the form of a word that is used to denote more than one
         [syn: plural, plural form] [ant: singular, singular
         form]

Moby Thesaurus II by Grady Ward, 1.0:

23 Moby Thesaurus words for "plural":
   a certain number, a few, certain, composite, dual, more,
   more than one, nonuniqueness, not singular, number, numerous,
   numerousness, pluralism, pluralistic, plurality, pluralness,
   plurative, several, singular, some, trial, variety, various



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

PLURAL. A term used in grammar, which signifies more than one.
     2. Sometimes, however, it may be so expressed that it means only one,
as, if a man were to devise to another all he was worth, if he, the
testator, died without children, and he died leaving one child, the devise
would not take effect. See Dig. 50, 16, 148; Id. 35, 1, 101, 1; Id. 3 1, 17,
4 Code, 6, 49, 6, 2; Shelf. on L 559, 589. See Singular.