The Collaborative International Dictionary of English v.0.48:

Brevity \Brev"i*ty\, n.; pl. Brevities. [L. brevitas, fr.
   brevis short: cf. F. bri[`e]vit['e]. See Brief.]
   1. Shortness of duration; briefness of time; as, the brevity
      of human life.
      [1913 Webster]

   2. Contraction into few words; conciseness.
      [1913 Webster]

            Brevity is the soul of wit.           --Shak.
      [1913 Webster]

            This argument is stated by St. John with his usual
            elegant brevity and simplicity.       --Bp. Porteus.
      [1913 Webster]

   Syn: Shortness; conciseness; succinctness; terseness.
        [1913 Webster]

WordNet (r) 3.0 (2006):

brevity
    n 1: the use of brief expressions
    2: the attribute of being brief or fleeting [syn: brevity,
       briefness, transience]

Moby Thesaurus II by Grady Ward, 1.0:

41 Moby Thesaurus words for "brevity":
   brachylogy, briefness, brusqueness, compactness, compendiousness,
   conciseness, concision, crispness, curtness, dumbness, economy,
   economy of words, instantaneousness, laconicalness, laconicism,
   laconism, littleness, lowness, muteness, obmutescence, pauciloquy,
   pithiness, pointedness, quietness, quietude, reserve,
   sententiousness, short time, shortness, silence,
   sparingness of words, speechlessness, succinctness, summariness,
   swiftness, taciturnity, terseness, transience, unloquaciousness,
   untalkativeness, wordlessness