Happening, as an occasional event, without regularity; coming without design; casual; accidental; hence, not of prime concern; subordinate; collateral; as, an incidental conversation; an incidental occurrence; incidental expenses.
An incident; that which is incidental; esp., in the plural, an aggregate of subordinate or incidental items not particularized; as, the expense of tuition and incidentals.
Incurred casually and in addition to the regular or main amount.
(frequently plural) an expense not budgeted or not specified; "he requested reimbursement of $7 for incidental expenses"
(sometimes followed by `to') minor or casual or subordinate in significance or nature or occurring as a chance concomitant or consequence; "incidental expenses"; "the road will bring other incidental advantages"; "extra duties incidental to the job"; "labor problems incidental to a rapid expansion"; "confusion incidental to a quick change"
following as a consequence; "an excessive growth of bureaucracy, with related problems"; "snags incidental to the changeover in management"
not of prime or central importance; "nonessential to the integral meanings of poetry"- Pubs.MLA