Vinculum \Vin"cu*lum\, n.; pl. L. {Vincula}, E. {Vinculums}. [L., from vincire, vinctum, to bind.] 1. A bond of union; a tie. 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} - vinc{x + y}.