Relating to, involving, or characterized by detailed scholarly inquiry and examination; of the nature of a disquisition.
From disquisition + -ary suffix (meaning 'relating to'), creating a variant adjective form with essentially the same meaning as disquisitional.
English speakers created BOTH disquisitional AND disquisitionary—two slightly different adjectival forms of the same noun, showing how redundant and exuberant English derivation can become!
Complete word intelligence in one call. Free tier — 50 lookups/day.