What is the definition of a special or extraordinary expense?

That list is exhaustive. If the claimed expense does not fit into any of those categories, it cannot be a special or extraordinary expense: Kase v. Bazinet, 2011 ONCJ 718 at para. 39.

Even where an expense fits into one of the listed categories, that is not the end of the story. The expenses must be both "necessary" -- as defined in relation to the child's best interests -- and "reasonable," as measured against the combined financial means of the parents (and, where appropriate, the child) as well as the family's spending patterns prior to separation: see section 7(1) and Yensen v. Yensen, 2003 BCSC at para. 8. In addition if the expense is one listed under subsection (d) or (f) -- educational programs or extracurricular activities -- the party claiming the expense must prove that they are "extraordinary."