I am interested in this unanswered question Pipe-fitting conditions in 3D and so I was trying to find information about it.
If the 3D curve $f(x(t), y(t), z(t)) = 0$ is a line I think that the pipe of diameter $D$ around it can be called the surface of a cylinder, but what is a proper mathematical term for describing that surface when $f$ is not a line? Tube? Pipe?