The Collaborative International Dictionary of English v.0.48:

Average \Av"er*age\, n. [OF. average, LL. averagium, prob. fr.
   OF. aver, F. avoir, property, horses, cattle, etc.; prop.
   infin., to have, from L. habere to have. Cf. F. av['e]rage
   small cattle, and avarie (perh. of different origin) damage
   to ship or cargo, port dues. The first meaning was perhaps
   the service of carting a feudal lord's wheat, then charge for
   carriage, the contribution towards loss of things carried, in
   proportion to the amount of each person's property. Cf.
   Aver, n., Avercorn, Averpenny.]
   1. (OLd Eng. Law) That service which a tenant owed his lord,
      to be done by the work beasts of the tenant, as the
      carriage of wheat, turf, etc.
      [1913 Webster]

   2. [Cf. F. avarie damage to ship or cargo.] (Com.)
      (a) A tariff or duty on goods, etc. [Obs.]
      (b) Any charge in addition to the regular charge for
          freight of goods shipped.
      (c) A contribution to a loss or charge which has been
          imposed upon one of several for the general benefit;
          damage done by sea perils.
      (d) The equitable and proportionate distribution of loss
          or expense among all interested.
          [1913 Webster]

   General average, a contribution made, by all parties
      concerned in a sea adventure, toward a loss occasioned by
      the voluntary sacrifice of the property of some of the
      parties in interest for the benefit of all. It is called
      general average, because it falls upon the gross amount of
      ship, cargo, and freight at risk and saved by the
      sacrifice. --Kent.

   Particular average signifies the damage or partial loss
      happening to the ship, or cargo, or freight, in
      consequence of some fortuitous or unavoidable accident;
      and it is borne by the individual owners of the articles
      damaged, or by their insurers.

   Petty averages are sundry small charges, which occur
      regularly, and are necessarily defrayed by the master in
      the usual course of a voyage; such as port charges, common
      pilotage, and the like, which formerly were, and in some
      cases still are, borne partly by the ship and partly by
      the cargo. In the clause commonly found in bills of
      lading, "primage and average accustomed," average means a
      kind of composition established by usage for such charges,
      which were formerly assessed by way of average. --Arnould.
      --Abbott. --Phillips.
      [1913 Webster]

   3. A mean proportion, medial sum or quantity, made out of
      unequal sums or quantities; an arithmetical mean. Thus, if
      A loses 5 dollars, B 9, and C 16, the sum is 30, and the
      average 10.
      [1913 Webster]

   4. Any medial estimate or general statement derived from a
      comparison of diverse specific cases; a medium or usual
      size, quantity, quality, rate, etc. "The average of
      sensations." --Paley.
      [1913 Webster]

   5. pl. In the English corn trade, the medial price of the
      several kinds of grain in the principal corn markets.
      [1913 Webster]

   On an average, taking the mean of unequal numbers or
      quantities.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Average \Av"er*age\, a.
   1. Pertaining to an average or mean; medial; containing a
      mean proportion; of a mean size, quality, ability, etc.;
      ordinary; usual; as, an average rate of profit; an average
      amount of rain; the average Englishman; beings of the
      average stamp.
      [1913 Webster]

   2. According to the laws of averages; as, the loss must be
      made good by average contribution.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Average \Av"er*age\, v. t. [imp. & p. p. Averaged (?); p. pr.
   & vb. n. Averaging.]
   1. To find the mean of, when sums or quantities are unequal;
      to reduce to a mean.
      [1913 Webster]

   2. To divide among a number, according to a given proportion;
      as, to average a loss.
      [1913 Webster]

   3. To do, accomplish, get, etc., on an average.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Average \Av"er*age\, v. i.
   To form, or exist in, a mean or medial sum or quantity; to
   amount to, or to be, on an average; as, the losses of the
   owners will average twenty five dollars each; these spars
   average ten feet in length.
   [1913 Webster]

WordNet (r) 3.0 (2006):

average
    adj 1: approximating the statistical norm or average or expected
           value; "the average income in New England is below that
           of the nation"; "of average height for his age"; "the
           mean annual rainfall" [syn: average, mean(a)]
    2: lacking special distinction, rank, or status; commonly
       encountered; "average people"; "the ordinary (or common) man
       in the street" [syn: average, ordinary]
    3: lacking exceptional quality or ability; "a novel of average
       merit"; "only a fair performance of the sonata"; "in fair
       health"; "the caliber of the students has gone from mediocre
       to above average"; "the performance was middling at best"
       [syn: average, fair, mediocre, middling]
    4: around the middle of a scale of evaluation; "an orange of
       average size"; "intermediate capacity"; "medium bombers"
       [syn: average, intermediate, medium]
    5: relating to or constituting the most frequent value in a
       distribution; "the modal age at which American novelists
       reach their peak is 30" [syn: modal(a), average]
    6: relating to or constituting the middle value of an ordered
       set of values (or the average of the middle two in a set with
       an even number of values); "the median value of 17, 20, and
       36 is 20"; "the median income for the year was $15,000" [syn:
       median(a), average]
    n 1: a statistic describing the location of a distribution; "it
         set the norm for American homes" [syn: average, norm]
    2: (sports) the ratio of successful performances to
       opportunities
    3: an intermediate scale value regarded as normal or usual; "he
       is about average in height"; "the snowfall this month is
       below average"
    v 1: amount to or come to an average, without loss or gain; "The
         number of hours I work per work averages out to 40" [syn:
         average, average out]
    2: achieve or reach on average; "He averaged a C"
    3: compute the average of [syn: average, average out]

Moby Thesaurus II by Grady Ward, 1.0:

136 Moby Thesaurus words for "average":
   Everyman, Public, accustomed, amidships, as a rule, average man,
   average out, avoid extremes, balance, banal, besetting, bisect,
   bourgeois, center, central, common, common man, common run,
   commonplace, conventional, core, current, customarily, customary,
   dominant, double, epidemic, equatorial, equidistant, everyday,
   everyman, everywoman, fair, fairish, familiar, fold, garden,
   garden-variety, general, generality, generally, girl next door,
   golden mean, habitual, halfway, happy medium, homme moyen sensuel,
   household, in the main, indifferent, interior, intermediary,
   intermediate, juste-milieu, mean, medial, median, mediocre,
   mediocrity, mediterranean, medium, mesial, mezzo, mid, middle,
   middle course, middle ground, middle point, middle position,
   middle state, middle-class, middle-of-the-road, middlemost,
   middling, midland, midmost, midpoint, midships, midway, moderate,
   no great shakes, norm, normal, normally, normative, nuclear,
   ordinarily, ordinary, ordinary Joe, ordinary run, pair off,
   pandemic, par, plastic, popular, predominant, predominating,
   prescriptive, prevailing, prevalent, rampant, regnant, regular,
   regulation, reigning, rife, routine, ruck, rule, ruling, run,
   run-of-mine, run-of-the-mill, running, so so, so-so,
   split the difference, standard, stereotyped, stock,
   strike a balance, suburban, take the average, typical, typically,
   undistinguished, unexceptional, universal, unnoteworthy,
   unremarkable, unspectacular, usual, usually, vernacular, via media,
   wonted