I am also taking this course (exam Saturday 17th EEK!). Basically, the example is of professors in a university. Along the top it has; Undergraduate, masters, phd, research, executive development, and community service. Along the side it has Accounting, administrative studies, finance, information and decision sciences, marketing, organizational behaviour, and quantitative methods. The definition in my book is "A structure that creates dual lines of authority; combines functional and product departmentalization." So basically, each person reports to two people in the heirarchichal structure, that of say the accounting department head, and the undergraduate program head, depending on what areas they fall under.
Hope that helps.