Two vectors 
and 
whose dot product is 
(i.e., the vectors are perpendicular)
are said to be orthogonal. In three-space, three vectors can be mutually perpendicular.
Orthogonal Vectors
See also
Dot Product, Orthogonal Basis, Orthonormal Basis, Orthonormal Vectors, PerpendicularExplore with Wolfram|Alpha
Cite this as:
Weisstein, Eric W. "Orthogonal Vectors." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/OrthogonalVectors.html