1) Metaphysics 2) Of or relating to ontology 
based upon being or existence
• (a.) Of or pertaining to ontology.
Ontology is a branch of philosophy. It involves the logical investigation of the different ways in which types of things (ie physical objects, numbers, abstract concepts, etc) are thought to exist, and the nature of various kinds of existence.
On`to·log'ic·al adjective [ Confer French ontologique .] Of or pertaining to ontology. 
[adj] - of or relating to ontology
ontology, ontological, ontologically, ontologist The philosophical study of the nature of being.
adjective of or relating to ontology; `ontological speculations`