Just to back up my version slightly, here are the first two definitions when you Google "define: forced labor":
"[...] a generic or collective term for those work relations, especially in modern or early modern history, in which people are employed against their will by the threat of destitution, detention, violence (including death), or other extreme hardship to themselves, or to members of their families"
"Work which one is compelled to perform against one's will, especially in a condition of involuntary servitude as a prisoner or slave"
[Emphasis mine in both cases.]
Neither of these really fit when talking about Israel's army conscription. There are some societal problems with not serving in the army (people look down on not serving, and sometimes people who haven't served have a harder time finding jobs,) but there's nothing approaching the level of what's talked about in those definitions I quoted.
Libertarianism (for example) argues for a particular zero, communism for a different one.
Different governments disagree on where it is appropriate to set this zero. Israel has chosen its position, and although somewhat unfortunate for Israelis, I don't believe this is a terrible choice.
Unless the salary they pay you is sufficient to induce you to join the army regardless of other penalties, it's forced labor. You are forced to perform labor you would not otherwise perform.