While "Indiscriminate Terrorism" would certainly be a useful term it appears to have the same meaning as "Terrorism" by the U.N.'s own definition so...not really.
The problem there is that the UN definition of terrorism comes from the general assembly, and the term 'indiscriminate terrorism' comes from the Comission on Human Rights. The various committees in the UN have come up with at least 27 different definitions of 'terrorism'. Yeah, it's screwy.
Here's another possible term for you: Bruce Hoffman, in the article The Modern Terrorist Mindset, deliniates two different versions of terrorism: left-wing and right-wing. Left wing terrorists make attacks on specific targets with assasination or kidnapping -- their very precise and planned. Right-wing terrorist are more willy-nilly, using large bombs, and killing people just to kill people. Personally, I don't like the terminology, because of political confusion, but it's another classification you can use, if you want.
Terrorism works fine as a broad term, just not as the ONLY term. When you get back to your books let's see all the other words that refer to the meaningful subsets so that, at least on this forum, we can have clear communication on the subject. I, at least, am interested to know them. That was the real point of this thread after all.
Here are some basic qlassifications. These come from Thomas O'Connor.
Terrorism Classified by Place1. Domestic -- by residents of a country within that country
2. International -- by representatives of a country against another country
3. Non-state -- extremism and revolution for its own sake
4. State-sponsored -- by a government against its own people or in support of international terrorism against another government
5. Internecine -- conflict that spills over into another country or fought on foreign soil
Terrorism Classified by Purpose1. Political -- for ideological and political purposes
2. Nonpolitical -- for private purposes or gain
3. Quasi-terrorism -- skyjacking and hostage taking
4. Limited political -- ideological but not revolutionary
5. Official or state -- used by nation against nation or people
Terrorism Classified by Issue1. Revolutionary -- aims to replace the existing government by drawing out repressive responses which can be exposed as inhumane (Red Army Faction, PLO, Hizballah)
2. Political -- heavily armed groups tending to be focused around supremacy, government intrusion, or religious revisionism (Aryan Nation, Posse Comitatus, Freemen)
3. Nationalist -- promotes the interests of a minority or religious group that has been persecuted under majority rule (Sikh radicals, Muslim fundamentalism)
4. Cause-Based -- groups devoted to a social or religious cause using violence to address their grievances (Islamic Holy War, Abortion clinic bombings)
5. Environmental -- groups dedicated to slowing down development they believe is harming animals (Animal Liberation Front, Earth 1st)
6. State-sponsored -- when a repressive regime forces its citizens into total obedience (Brazil, Colombia, Guatemala, Honduras, Peru, Iraq, Sudan, Haiti)
7. Nuclear -- outlaw states possessing nuclear threats (Libya, North Korea)
8. Genocide -- when a government seeks to wipe out a minority group in its territory (Cambodia, Rwanda, Bosnia, Iraq, Turkey)