Anyhow, suicide or Khudkushi means ... killing oneself intentionally and that could be done by any means. If a person acts with intention of killing himself than that action is suicide, regardless of that person lives or die. Intention before getting killed is important. As long as there is an iota bit of chance in the belief of the person (rightly or wrongly) that his initiated action may not kill him and he might live, than that action can be classified as not suicide even though it may look like suicide to others. But there is no chance that a person blowing himself could not be called suicide.
Not that I support these radicals, but the logic they use to rule suicide bombing as permitted is rooted in the Islamic principle that neccessity overrides prohibition.
In this case, the logic used is that suicide is definately haraam, and ordinarily strapping explosive to yourself and letting them off would be a grave sin. But if in a jihad, you lack effective weapons to fight, and suicide bombings are the most effective means at hand, then they are no longer haraam.
These rulings were rooted in the Israeli-Palestine conflict. Israel had planes and helicopters and tanks that could make targetted attacks anywhere in the Palestians lands and cities, and the Palestinians had none of these. The only effective explosive delivery mechanism they had was the human body. Back then, scholars ruled that this neccessity meant suicide bombing was ok.
Today, we are seeing so-called "jihads" being waged even against Muslim societies such as Pakistan, Afghanistan and Iraq, but the same logic of fatwas has been applied.
As I mentioned before, the only solution is to get to Maulvis and imams propounding extremist views, and get them to renounce those views or kill them.
Frankly, this is how the Ottoman Khalifat deal with extremists such as those from Arabia who raided Shia shrines in Ottoman-controlled Iraq. This is the model that just be applied today.