1. constituting a beginning; giving origin to something derived or developed; original; elementary.
2. Embryology: first formed.
3. pertaining to or existing at or from the very beginning.
Etymology: from Late Latin prīmōrdiālis, “of the beginning, original”, from Latin prīmus, “first” + ōrdīrī, “to begin”.
[Freydoon Rassouli - In The Beginning]