Odlov: To be honest, it doesn't matter. It's just a friendly little thing to converse about.

Is Smoking Suicide: That depends, are you insisting it would be right to arrest someone for a homicide because they are smoking in a room which could potentially give off second hand smoke which could potentially kill people. And you know it.

Is joining the army: It can potentially kill you; however, it's not an assured death. The gunman is assuring your death if you say yes or nothing. Being placed in a situation where there is a risk that you may die isn't intentionally dieing. Now if you are assured by your general that by going to x location with y protection you will die, and you choose to go to x location with y protection, that would arguably be a form of suicide.

Is Driving Drunk Suicide: Again, it's not an assured death. Just like eating junk food.

Potential = Assured is different. Driving a car isn't a form of suicide, even though statistically you have a decent chance of being in a fatal accident within your lifetime. Eating bread isn't suicide because you can potentially choke on the bread and suffocate.

When someone knowingly enters a situation where without reasonable doubt they will be killed and they enter the situation by choice anyways, that could be a more concrete term for the real definition of suicide, which would coincide simply taking "the coward's way out". Thus eating, drinking, driving, etc. Aren't forms of suicide. Nor joining the army, nor smoking.