Israel has clearly defined borders. If youre are talking about the West Bank there’s area a, b and c which are controlled by Israel, both, and PA respectively. I’d call that borders.
Israel has never defined its own borders. This is easily googleable. There are borders that are well understood by the international community but it is a fact that the state of Israel itself has never defined it's own borders.
Sure and they exercise sovereignty far beyond those borders in a blatantly illegal manner. They do not acknowledge their de facto borders because it would be admitting to acts the world would be required to condemn to maintain the pretense of law and order.