Is smoking suicide? It can potentially kill you and you know it.
Is joining the army suicide? It can potentially kill you and you know it.
Is driving drunk suicide? Eating junk food?

It all comes down to your personal intention. If i join the Army with a death wish, hoping to get shot in the hottest conflict zone, then I am committing suicide. Outsiders who don't know my motives could never tell, but ultimately it was.

PS: and why does it matter?