Final answer:
Baruch Spinoza, a well-known rationalist philosopher, embraced ontology, the study of being, existence, or reality, as opposed to the broader term metaphysics. His dedication to reason and structured thought reflects an ontological approach, as can also be seen in his influential work, Ethics.
Step-by-step explanation:
The rationalist philosopher who preferred the term ontology over metaphysics is none other than Baruch Spinoza. Spinoza, a rationalist thinker along with Descartes and Leibniz, believed in a form of rational thought that was deductive and abstract, much in contrast to the scholastic tradition prevalent before the Enlightenment. Spinoza's most renowned work, the Ethics, is indicative of this, employing a method that mirrors the geometric system of Euclid's Elements. In the broader scope of philosophy, ontology deals specifically with the study of being, existence, or reality, whereas metaphysics encompasses a wider range of philosophical inquiry into what exists. While Spinoza's embracing of ontology over metaphysics isn't explicitly documented, his intellectual legacy within rationalism is marked by a commitment to reason and structured thought, principles that are fundamentally ontological in nature.