The Collaborative International Dictionary of English v.0.48:

Vacuity \Va*cu"i*ty\ (v[.a]*k[=u]"[i^]*t[y^]), n. [L. vacuitas.
   See Vacuous.]
   1. The quality or state of being vacuous, or not filled;
      emptiness; vacancy; as, vacuity of mind; vacuity of
      countenance.
      [1913 Webster]

            Hunger is such a state of vacuity as to require a
            fresh supply of aliment.              --Arbuthnot.
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   2. Space unfilled or unoccupied, or occupied with an
      invisible fluid only; emptiness; void; vacuum.
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            A vacuity is interspersed among the particles of
            matter.                               --Bentley.
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            God . . . alone can answer all our longings and fill
            every vacuity of our soul.            --Rogers.
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   3. Want of reality; inanity; nihility. [R.]
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            Their expectations will meet with vacuity.
                                                  --Glanvill.
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WordNet (r) 3.0 (2006):

vacuity
    n 1: the absence of matter [syn: vacuum, vacuity]
    2: a region that is devoid of matter [syn: vacuum, vacuity]
    3: total lack of meaning or ideas [syn: inanity,
       senselessness, mindlessness, vacuity, pointlessness]

Moby Thesaurus II by Grady Ward, 1.0:

34 Moby Thesaurus words for "vacuity":
   bare, bareness, barrenness, blank, blankness, bleakness, cavity,
   clear, desolateness, dull, dullness, emptiness, empty,
   empty-headed, foolish, hollow, hollowness, inane, inanity, nada,
   nihility, nonexistence, nullity, shallow, silly, stark, stupidity,
   superficial, vacancy, vacant, vacuous, vacuousness, void,
   voidness