The definition – one of the most complex things in life is arriving at definitions – if I say a person is a body, that doesn’t define really the spirit etc. – so to arrive at the definition of the unknowable unseen God is practically impossible, however God gave us a hint, for firstly it is written, God says "I have given you my soul, within the Torah"; if this is the case within the revealed dimensions of the Torah certainly within the soul/esoteric; furthermore we know Tzaddikim mirror their Creator so if a. mirrors b. then b. mirrors a., we have had the merit in our lifetime and the past 9 generations, extraordinary Tzaddikim (saints) and all one can say is what Kabbalah itself describes about God, that apart from his essence being sensitivity, compassion, kindness (as our sages already say and as God says about himself, that He is) nonetheless referring (to the "abilities") expressions of God, He is called shlemusah dikulah, perfection in all details – hence the body is perfectly made, as is nature, as his his wisdom, as his system – namely, that we are born into darkness, then from our own accord seek light and then eventually enter into a perpetual growth cycle