Of or pertaining to an accessory, e.g. to a crime.
Of or relating to an accession.
Assessorial.
An assessorial charge.
Existing tangentially, being a byproduct, a tangent, or a likely consequence.
Entering or approaching, prior to reflection (more frequently incident).
Occurring by chance.
Loosely associated; of limited relevance except indirectly; only accidentally related.
Something that is incidental.
Minor items, not further defined. Incidental expense.