The Collaborative International Dictionary of English v.0.48:

Vinculum \Vin"cu*lum\, n.; pl. L. Vincula, E. Vinculums.
   [L., from vincire, vinctum, to bind.]
   1. A bond of union; a tie.
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   2. (Math.) A straight, horizontal mark placed over two or
      more members of a compound quantity, which are to be
      subjected to the same operation, as in the expression
      x^2 + y^2 - vincx + y.
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   3. (Anat.) A band or bundle of fibers; a fraenum.
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   4. (Zool.) A commissure uniting the two main tendons in the
      foot of certain birds.
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