The Collaborative International Dictionary of English v.0.48:

Sobriety \So*bri"e*ty\, n. [L. sobrietas: cf. F. sobri['e]t['e].
   See Sober.]
   1. Habitual soberness or temperance as to the use of
      spirituous liquors; as, a man of sobriety.
      [1913 Webster]

            Public sobriety is a relative duty.   --Blackstone.
      [1913 Webster]

   2. Habitual freedom from enthusiasm, inordinate passion, or
      overheated imagination; calmness; coolness; gravity;
      seriousness; as, the sobriety of riper years.
      [1913 Webster]

            Mirth makes them not mad,
            Nor sobriety sad.                     --Denham.
      [1913 Webster]

   Syn: Soberness; temperance; abstinence; abstemiousness;
        moderation; regularity; steadness; calmness; coolness;
        sober-mindeness; sedateness; staidness; gravity;
        seriousness; solemnity.
        [1913 Webster]

WordNet (r) 3.0 (2006):

sobriety
    n 1: the state of being sober and not intoxicated by alcohol
         [syn: soberness, sobriety] [ant: drunkenness,
         inebriation, inebriety, insobriety, intoxication,
         tipsiness]
    2: moderation in or abstinence from alcohol or other drugs [syn:
       sobriety, dryness]
    3: a manner that is serious and solemn [syn: graveness,
       gravity, sobriety, soberness, somberness,
       sombreness]
    4: abstaining from excess [syn: sobriety, temperance]

Moby Thesaurus II by Grady Ward, 1.0:

147 Moby Thesaurus words for "sobriety":
   abnegation, abstemiousness, abstention, abstinence, augustness,
   balance, blackishness, calm, calmness, common sense, conservatism,
   constraint, contact with reality, continence, control, cool,
   cool head, coolheadedness, coolness, courtliness, darkishness,
   darkness, darksomeness, decorousness, demureness, denial,
   dignifiedness, dignity, dispassion, due sense of, duskiness,
   duskness, earnestness, evenness, forbearance, formality, frugality,
   funereality, gentleness, golden mean, good sense, grandeur,
   graveness, gravity, grimness, happy medium, healthy mind,
   horse sense, impartiality, judiciousness, juste-milieu, kingliness,
   lenity, level head, levelheadedness, loftiness, long face,
   lordliness, lucid interval, lucidity, majesty, meden agan,
   mental balance, mental equilibrium, mental health, mental hygiene,
   mental poise, middle way, mildness, moderateness, moderation,
   moderationism, neutrality, nobility, nonviolence, normalcy,
   normality, normalness, nothing in excess, pacifism, plain sense,
   practical mind, practical wisdom, practicality, pride of bearing,
   pride of place, princeliness, proud bearing, prudence, rationality,
   reason, reasonableness, regality, renouncement, renunciation,
   repose, restraint, right mind, sadness, sanemindedness, saneness,
   sanity, sedateness, self-abnegation, self-control, self-denial,
   self-discipline, self-mastery, self-restraint, sense, senses,
   sensibleness, serenity, seriousness, sober senses,
   sober-mindedness, soberness, sobersidedness, sobersides, solemnity,
   solemnness, somberness, sophrosyne, sound mind, soundness,
   soundness of mind, stability, staidness, stateliness, steadiness,
   straight face, swarth, swarthiness, swartness, teetotalism,
   temperance, temperateness, thoughtfulness, tranquillity,
   unexcessiveness, unextravagance, unextremeness, venerability,
   via media, weightiness, wholesomeness, worthiness