TL;DR
In this post we explain definition of structural testing approach that is given by Black Box Software Testing Foundations course (BBST) created by Rebecca Fiedler, Cem Kaner and James Bach.
Definition
As we have already wrote in our previous post There are no correct software testing definition, same term could have different meaning for Agile project members. You as a tester should always ask clarification question about any term introduced in project. In that way, you put all project members on same page.
Sometimes different terms have same meaning. Structural testing is an example.
Structural testing is testing or test design using knowledge of the details of the internals of the program (code and data).
Structural testing is synonym for Glass box testing.