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.
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   2. Contraction into few words; conciseness.
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            Brevity is the soul of wit.           --Shak.
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            This argument is stated by St. John with his usual
            elegant brevity and simplicity.       --Bp. Porteus.
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   Syn: Shortness; conciseness; succinctness; terseness.
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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]