“Know that there is no deed that is not an affair of wujūd, and there is no affair of wujūd that does not signify the wujūd of God and His tawhīd, whether the affair is blameworthy according to common consent and the Shari`ah, or praiseworhty according to common consent and the Shari`ah.
~ existence, concretion, actuality
Then it can be seen that from our human perspective, we are held to affirm on the one hand the absolute unlikeliness of Allah with anything created, this 'perspective' is called tanzīh or absolute transcendance of God (in Western Metaphysics, where tanzīh is obviously not as clear as in Islam, which gave rise to serious misconceptions) and on the other hand (to affirm) the likeliness of Allah with creation, tashbīh.
So that man can conceive at least (somewhat of) Allah's names or Allah's qualities.
For example: He is the All-Merciful, the All-Compassionate. When we learn how in the animal kingdom, a mother bird takes care of her beloved child, so we immediately conceive the idea of • compassion •, although the whole reality of it will still escape us, and we will fall short of it.
Further wahdat-ul wujūd is really `ain al wujūd (the essence of being, existence), meaning nothing really exists than the Real (Allah), because everything else has only a limited, defined wujūd.
It seems that Ibn `Arabi never used wahdat-ul wujūd, instead 'ain al-wujūd, but whatever the term, as long as one knows what is behind.
And Allah knows best and most.