This should not be a difficult one!
Philosophically define God.
on your mark get set…GO!
It isn’t difficult - it is utterly impossible
God cannot be defined - but can be known, though* extremely *incompletely
The notion of “defining” God is itself not applicable - for only what is finite, that is, what has *fines *(= limits), can be de-fined. Concepts referring to God can be helpful, but they are not themselves God. It is much easier to say what God is not, than to say what God is. It is also possible to ascribe certain attributes to Him - but He infinitely exceeds what can be known of Him; He is God, not a bundle of ideas about God. All our thoughts about Him are miserably short of the Reality
Besides, human language is also limited - it hasn’t the resources to speak of the God Who is “beyond” limit; it cannot avoid stumbling & stuttering, because it is both itself limited, & is spoken by us limited beings. This is why Christian faith is in a Person, & not in anything made of words; & why revelation & faith are so important in Christianity.
If the reality of human persons cannot be exhausted by what is said about them, how much more is this true of God, Who is God
and, is Three-Personed !
As has been said already in the thread: “God is”.