My definition of terrorist tactics is irrelevant to how the OP would classify Hamas.
Regardless, here’s how terrorism is defined on Wikipedia: it seems pretty reasonable to me.
Terrorism, in its broadest sense, is the use of violence against non-combatants to achieve political or ideological aims. The term is used in this regard primarily to refer to intentional violence during peacetime or in the context of war against non-combatants
A Very Brady Sequel.