It’s no great mystery what genocide is in the context of the UN’s International Criminal Court.
Opinion
Article II
In the present Convention, genocide means any of the following acts committed with intent to destroy, in whole or in part, a national, ethnical, racial or religious group, as such: (a) Killing members of the group; (b) Causing serious bodily or mental harm to members of the group; (c) Deliberately inflicting on the group conditions of life calculated to bring about its physical destruction in whole or in part; (d) Imposing measures intended to prevent births within the group; (e) Forcibly transferring children of the group to another group.
I'd say Israel is unquestionably doing a, b, and c. There's a strong argument to be made that the utter destruction and targeting of hospitals for bombing constitutes D. AFAIK they're not doing E. But here's the thing: only one of those points needs to be true to qualify as a genocide.
Well the UN has a definition, it's really narrow (they did it on purpose to let a lot of their members who did genocide off the hook) but it's at least a starting point. Generally speaking, it's when your intent is to wipe out a people, either through outright murder or cultural erasure.